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Using a Repeat Timer with setInterval
2:27In this video, we'll use a repeat timer in the form of the `setInterval` function to modify the display of a clock.
The setTimeout function only
runs the callback one time.
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There is another function will repeatedly
call a call back after a delay
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continually.
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And that's the setInterval function.
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Now that we're used to a one off timer,
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we're going to use a repeat timer
to build a clock like this.
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Open the workspace
accompanying this video.
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In the clock.js file there's
some JavaScript code already.
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First, let's select in this section
element with the ID of clock on the page
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and assigning it to
the clockSection variable.
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Then we have a getTime function that
formats some time from today's date.
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The getTime function represents
a string that represents the time.
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Finally we have the tickClock
function that displays the clock.
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Click on the preview and
you'll see the text clock goes here.
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Open up the developer tools and
you can call tickClock manually.
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Instead of me calling the tickClock
function over and over again myself I can
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use this set interval function to
execute the callback every second.
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Remember one second is 1,000 milliseconds.
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Save the clock and then preview.
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We see clock goes here for
one second, and then the clock ticks.
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This is because the set interval
function starts after the delay.
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And is not invoked immediately.
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To get around this, we can call the
tickClock function immediately ourselves
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when the page loads, and then let the
setInterval do it every second afterwards.
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Okay, I have another challenge for you.
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Can you try and
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use an anonymous function with these
set interval in the clock application.
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If you try and can't, can you explain why?
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I'll share with you my thoughts and
the solution next.
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