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Now that we've seen the basics of the promised syntax we're gonna go ahead and explore how we can update

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documents using Mongo D.B..

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And we're gonna do so with promises instead of callbacks.

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So to start I'm going to close both of the open files from the playground directory and I'm going to

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bring my tree view back into view from here.

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The only file we need access to is the one we've been using mostly in this section.

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Mongo D.B. dot J S now down below.

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We do want to switch the terminal directory as well.

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I'll use CDE dot dot forward slash task manager to switch over to that folder and I'll just use clear

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to clear the terminal output so we know how to create documents we can use insert one and insert many.

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We know how to read documents we can use find and find one.

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And for update we use UPDATE 1 and update many.

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Let's go ahead and explore them down below.

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I'm gonna remove all the code for find once again that's always available inside of the PD f guide for

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that lecture and down below.

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We're gonna start to update our documents to start let's go ahead and switch up someone's name.

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So inside of our database I have a collection of users.

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And right here as an example I have to Andrews I'm going to go ahead and adjust one of those to be something

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else.

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So what I'm going to do is target this second Andrew by I.D. and I'll update his name to something like

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Mike over in the API docs.

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We have two of the methods we'll be using for collection if we scroll down near the end for you we have

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Update 1 for updating one document and update many for updating multiple.

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There's also this update method that's been deprecated.

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It's an old way to update documents and it's going to be removed in a future version.

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You should either be using update many or update 1 depending on what you're trying to do.

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Now we'll start with UPDATE 1 to update just that one document.

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The first object we provide is the filter.

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So we target the one document we're trying to update we'll target it by I.D. so we could target it by

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any other field value.

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Then we have the updates we're trying to apply.

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Now there's also this optional options object which we're going to skip like we've been doing so far.

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And we have our callback as the third argument now for this.

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We're actually not going to use a callback.

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We're gonna use a promise.

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And down below I can see under its return value it returns a promise if no callback is passed in.

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Let's go ahead and actually use this first up I do need to grab the idea of the document I'm trying

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to update I'm gonna go ahead and right click this document to click edit so I can copy the I.D. value

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then I'll bring that over to my application code.

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So over here we're gonna go ahead and use Update 1 and to update just that one document.

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Now it still starts off these same way.

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So D.B. dot collection I'm trying to update a document in that user's collection and I'm gonna go ahead

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and use the update one method which we just explored.

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Now the first object this is where we provide the search criteria.

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So in our case we're going to target the document by its I.D. and the I.D. is going to equal a new object

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I.D..

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And we're gonna go ahead and pass to it as its first and only argument the string value we copied from

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robo.

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3 T.

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So in this case we're creating an object I.D. using an existing value.

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And that's how we're gonna be able to target our documents accordingly.

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Now that we're targeting the document correctly we can go ahead and move on to the second argument for

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Update 1.

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This is the actual updates we want to apply.

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Now this is where things get a bit different from what you might expect.

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We don't just change things right here like setting name equal to Mike.

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Instead we use what are known as update operators to define the behavior we want to perform.

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We'll pull up the documentation for the update.

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Operators in a moment.

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Let's just start with the most common one which is dollar sign it's set.

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And this operator allows us to set new values for the fields in our document.

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And right here we're gonna go ahead and provide it an object value which is what it expects from here

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we can customize the fields like name or age.

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In this case I just want to customize the name of the document and I'll go ahead and set it to something

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new.

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That's not Andrew like Mike.

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Perfect.

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Now it's important to note that when we use set and we don't provide a field it's not going to delete

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it.

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In this case it's only impacting the fields we've explicitly listed out.

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Nothing's happening to age.

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Age is going to stay exactly as it is now if we were using the callback pattern we would go ahead and

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provide a third argument to update 1.

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This would be the function and we would get access to either the error or the result when we're using

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promises though we don't provide that function.

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Instead what Update 1 returns is indeed the promise.

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So right here we can create a new variable update promise as an example and down below we can go ahead

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and use some of the methods available on it right here.

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That would be update promise then to register a function to run when things go well and the document

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is updated and then down below we can set up a call to catch to register a function for when things

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fail.

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Now for the success case when the promise is fulfilled we'll get access to the result.

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And when the promise is rejected we'll get access to the error and for both we'll just log them to the

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terminal consult that log printing the result up above then down below.

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The same thing console dot log printing the error.

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Excellent.

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Now when we run this we're actually going to see the name field update over in robo 3.

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If I give things a quick refresh I can see the name still is Andrew down below.

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I'm gonna run the script node Mongo D.B. dot J.

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S to fire things off right here.

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We got a bunch of output and then over inside of robo three T.

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If we take things another refresh right here I can see the name has been updated to Mike so the output

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we're getting is all of the things available on result.

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And the only field we would ever pull off of there is modified count or possibly matched count matched

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Count is always going to be 1 or 0 for our update.

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One calls and modified count is going to be 1 or 0 1 if a document was modified and 0.

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If no document was modified so that's how we can use.

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Update 1 to update a document.

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Now we can also change this syntax.

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What we don't have to do is create a variable update promise and then add those method calls on there.

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We can actually change all of this together.

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So what does that mean.

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It means this variable can be deleted and down below we can add our dot then call right on to the end

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of the closing parentheses for update 1.

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So it's D.B. dot collection Dot.

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UPDATE One dot then dot catch.

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And this is a very common pattern.

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We're going to see throughout the class and that you're going to see as you start to work with a synchronous

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javascript whether that's on the front end or whether that's inside of node j.

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As this is a very common promise pattern.

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Now let's pull up the complete list of update operators so we can see what we have available to us.

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Aside from just set what I'm going to do is head over to the browser and what we're looking for is actually

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not part of the API documentation but we can crack open a new browser tab to find it right here.

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What I'm gonna do is Google Mongo D.B. update operators.

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This is going to bring us over to the correct article on the reference documentation.

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Right here we have the list of update operators.

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And if we scroll down a bit on this page it's going to bring us to a nice long list of operators which

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start with the dollar sign.

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So down below we have set which we already used and we have other nice ones as well.

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For example unset to remove a specific field from a document or rename to rename a field.

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We also have other ones that aren't quite as common including things like increment or ANC for short

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which allows you to increment a number in a particular document.

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We could use this as an example to increment the age.

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So these are some of the various ways we can work with our documents though in almost all cases you'll

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be using set.

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If you're trying to change the field value which is the most common scenario.

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The second most common would be to use increment.

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So let's go ahead and explore that.

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If we had over two robo three Ts we can see that Mike has an age of twenty seven.

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Let's go ahead and increment that to 28 from the visual studio code.

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Ed I'm gonna remove the set operator and we are going to use I N C instead.

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Now we can actually click the INEC operator in the documentation to learn how it works if we click on

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that it brings us over to some examples.

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Here we can see that we provide the field and the amount we want to increment by.

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So let's get that done.

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Now the only field we can actually increment is the age and we can increment in a positive way by using

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a positive number.

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Or we can decrement by using a negative number.

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In this case let's use one to increment the age by 1.

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I'm going to save Mongo DB.

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J S I'm going to rerun the script from the terminal down below.

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And if we had over two robo three TI we should see that age changed right here it was twenty seven I

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refresh things and it's now twenty eight.

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So those update operators allow us to do a lot of interesting things without needing to do more heavy

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lifting if we didn't have access to this operator we would have to read the document out of the database

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figure out what the current age is increment it and then use another operation to update the document.

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So that would be a fetch and an update with the increment operator.

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We can do all of this at once saving resources and getting things done just a bit quicker.

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Now it's challenge time it's going to be up to you to use update many which works very similarly to

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update 1.

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So instead of updating one it updates many as the name suggests.

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So I'm going to comment out all of the code for our update one call.

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So it doesn't keep incrementing that age though I'll leave it in place as a reference for the moment

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and down below.

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I'll paste in those challenged comments.

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So your goal is to use update many to complete all of the tasks.

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So we have our tasks collection over in robo 3D.

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I'll give things a quick refresh to make sure we're looking at the latest data.

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I have three tasks.

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One is complete the other two are not we want to use the update many operation to update all documents

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to be complete so when they're done I should see completed it true for everything.

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Now we can do that in one call with just update many as opposed to multiple with.

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Update 1.

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And that's exactly what you're going to do as your challenge.

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So step 1 Check out the documentation for update many to get comfortable with how it works.

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Hint It's kind of be pretty familiar to what we just learned about with Update 1.

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Then you're going to set up a call with the correct query and your updates using the necessary update.

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Operator And then you're going to use the promised methods to set up these success and error handler

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functions.

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And finally you're going to test your work.

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You should be able to run the file just a single time refresh things over in robo 3 T and see completed

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true for everything.

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Now with all of your tasks are already completed or you mess up and you need to get better sample data

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you can just right click one of your tasks edit it and switch the completed value over to false and

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rerun your script to make sure it's working.

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All right take some time to knock that out test your work and when you're done come back and click play

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how'd that go.

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Let's kick things off with step number one.

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Check out the documentation for update.

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Many now it's not a method we've used before but it is similar to methods we've used before and the

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goal of working through this section and through these challenges is not to talk about every single

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thing that Mongo D.B. can do because the course would become two hundred hours long and most of it would

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be terribly boring.

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The goal here is to give you the stuff that's essential to creating real world applications and to give

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you the tools and know how to explore the other things.

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When you're ready so down below we can go over to the update.

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Many docs and we can see that the first argument is our filter.

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The second is our updates.

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Then we have the options which we don't need.

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And we have our callback which we're not going to provide because we get a promise back if no callback

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was passed.

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Let's go ahead and knock this out over here.

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I'm gonna set up the call with the query and the updates.

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That's D.B. dot collection.

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We are updating the documents in tasks.

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I'll be using update many and I'm going to provide those two arguments.

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First up we are going to find all tasks where completed is equal to False that's complete.

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Don't forget the d..

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Otherwise it won't work as expected.

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Perfect.

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Then we're going to provide that second object.

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This is the list of operations we want to perform now in our case we just want to set a field value

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so I will use set and we are going to set completed equal it to true.

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So find the docs where completed is false.

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Set it over to a completed value of true.

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That's step 2 step 3.

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Use the promised method to set up our handlers dot then right here.

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Here we will get access to the result and then down below we can add a call to catch where we will get

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access to the error should that promise get rejected perfect.

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Now if the promise is fulfilled what are we going to do.

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We'll just dump that result again.

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Actually we can just dump something like the modified count.

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Now you didn't need to dump the same thing to the council if you just printed result.

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That's perfectly fine right here result.

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Dot modified count.

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Perfect.

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Next up down below for the error.

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We will just print that in its entirety.

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And now we can go ahead and test things out.

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So we looked at the docs we set up the call.

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We set up the promised handler methods and now it's time to test the work.

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Now I'm going to pull up robo three ti one more time and give things are refreshed just to make sure

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the data is what I expected.

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We have two tasks with the completed value of false and from the terminal down below.

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We'll run our script.

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I'm going to run it.

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I can see that I have two documents updated which does sound right.

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00:15:30,760 --> 00:15:34,730
And if I refresh things over in rowboat 3 T what do I see.

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I see that all of my tasks are now completed.

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Which is fantastic.

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So there we go.

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Challenge complete.

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We were able to use this new method to achieve the desired result.

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Now we can remove the challenge comments and that's where we're gonna stop for this one in the next

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video.

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We're going to move on to the final letter in crud.

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I know how to create I know how to read and update.

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It's time to learn how to delete documents when we're done with them or they're no longer needed.

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We're gonna cover that next.

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So let's jump right in.