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Removing Names
7:43What if users make a mistake and want to remove a name? Let's add a button to each list item to delete it. We'll also move to a delegated click handler, to allow us to set one handler for all buttons.
All right, so
our app is really starting to take shape.
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So our next task is to provide a way
to remove invitee names from the list.
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Let's add a remove button
to each list item, so
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that clicking the button deletes the name.
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Over in app.js, the first step will take
is adding the remove button as a child
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of each list item, right below the label
and check box we added in the last video.
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In fact, the code to do this will be so
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similar to the code we used to create,
edit and append the checkbox element.
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So I'll copy these three lines of code and
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paste them right below where
we append the label to li.
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So in this new code we'll change
the check box constant to button and
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change the element we're
creating to a button.
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In the next line we'll change
checkbox.type to button.type.
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And here we don't need to
change the buttons type, but
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we do need to set its text
content to be removed.
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So we'll change it to
button.textContent remove.
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And we'll also change label to
li because we want to append our
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button to the list item.
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All right, so now we've added a button to
each list item, let's save this file and
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test it out in the browser.
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So now when we add a name to the list,
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the remove button is added too, but
the button doesn't do anything yet.
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We need to add a handler to it,
so let's do that now.
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Over in our code, it makes sense
to use a delegated handler for
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removing items just like we did with
the check boxes in the last video.
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Because the user may add and
delete lots of names to the list.
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It's a good idea to use the parent
element to receive the event and
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handle what should happen when
the remove button is clicked.
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So just as we did in the last video,
we'll set an event handler on ul.
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And we'll handle click events that bubble
up when a user clicks one of the remove
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buttons.
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So in other words the click event is
initially received by the button but
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travels up the DOM to the li and
then the ul element.
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Now, since click events can be triggered
on all sorts of elements in the ul,
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we need to filter out
elements that aren't buttons.
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And we can do that with an if statement.
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So if the target elements
tag name is button,
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we want the code in our
if statement to run.
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Otherwise the events from
other elements are ignored.
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So now you might be wondering,
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well what if there are other
buttons besides remove buttons?
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How would we differentiate between this?
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We'll actually look at that
later in this course and
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we'll address that by reading
the buttons text content and you
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could also set class names on the buttons
and read those to differentiate them.
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But for now let's just get the one
remove button we have working.
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So inside the if statement,
we want to remove
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the list item from the an ordered
list using the remove child method.
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And we can get a reference to
the list item from the buttons
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parent node property.
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So let's assign that to
a variable we'll call
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li,then we'll say e.target.parentNode.
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Then from here we can traverse
to the list items parent node.
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So let's create a ul const and
say li.parentNode.
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And once we have these two elements,
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we'll call remove child on
the ul passing in the li.
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All right, let's save this and test it out
in the browser and see if it's working.
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I'll just refresh and enter a few names.
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Let's say Joel, Alena and Faye.
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And then let's try removing them.
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I'll click the remove button for
Alena, and Joel and
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great we see that it's working.
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So now let's just take a look at our
submit handler at the top of app.js and
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notice that it's starting
to look a little long.
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That makes it more time consuming to
read and potentially more confusing for
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other people looking at our code.
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So if we break this code
up into separate functions,
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for example, our code will be
easier to read and understand.
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It'll also be more modular since
we'll create small chunks of code
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that we could potentially
reuse pretty easily.
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So let's think about how we could
break the submit handler up a little.
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When the user submits the form we cancel
the browsers regular submit behavior and
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store the input value from the text
field then we clear the input.
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Those actions are related to this submit
handler but notice the next section here.
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The lines here create a list item element
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which is added to the DOM
on the last line.
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So we could write a function that takes
the text we want the list item to contain
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and returns that list item back to us.
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That would make this handler a lot
simpler to read and understand.
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So I'm going to select these lines.
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So line 9 through 19 and
cut them out of this function and
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use them in a new function.
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So first right above
the append child method,
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I'll write out a function name
I think makes sense for this.
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I'll name it createLI.
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And I'll pass in the text and
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store the output of this
function to the variable li.
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So now this handler is a lot
easier to read without those other
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distracting lines.
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Next right above this handler,
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let's write a function named createLI,
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passing in text as a parameter.
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And inside the function we'll
paste the code we cut out.
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So at the top of this function,
we create the list item element,
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then we assign the value
of text as it's content.
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And notice that we named
the function's parameter text,
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which means we don't have to rename the
text variable in the lines we pasted in.
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So now the only thing we need to add
to this function is a return statement
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at the end to return the list
item element to the handler.
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Because without a return statement
JavaScript functions return
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undefined, but a fault.
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So great, now we have a logical task
that's separated into its own function,
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which will make this code a lot
easier to read and understand.
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Let's save our file and test our code in
the browser, to make sure it still works.
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We'll add some names to the list,
click Confirmed Remove,
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and cool, we see that it works just fine.
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All right, so nice work so far.
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Our users can add new names,
remove names and check out for responses.
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Now if our users make a typo, it would
be nice if they could edit the names.
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And I'll show you how to do that
in the next part of this course.
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