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The Console API
3:48The Console API is useful for profiling JavaScript code, logging commands, recording the execution time of code, and more. In this video, you’ll learn how to time the execution of a loop.
One other console command that I wanna
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show you is timing how long something
takes.
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This is good if you're trying to profile
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the performance of your JavaScript, and
you wanna profile
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beyond CPU usage and memory, and you
actually just
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wanna see how long something is taking to
execute.
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So I'm going to write a function here, and
I'm going to say MyLogTest.
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And I'm going to pass it a variable.
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And inside of here, I'm going to say
console.time.
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And I'm going to pass that string to say
Loop.
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By the way, to hit Enter in my console and
skip down to the next line,
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without actually executing this I'm just
holding down Shift, and hitting Enter.
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And that can break down to the next line.
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Next I'm gonna create another for loop
which is endless here.
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That's actually not great practice, you
shouldn't
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do that because oftentimes the conditions
to end
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the for loop will never come, as you saw
earlier when I crashed my browser.
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But I'm gonna do it anyway for brevity.
So, MyVar is going to increment by one.
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I'm gonna say console.log.
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And inside of this, I'm going to
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use a little bit of JavaScript
concatenation syntax.
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So I'm gonna say, the value of MyVar is,
with a space and then a plus.
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And then I'm going to print the value of
my variable.
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And then, just because we want this to be
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nicely formatted, I'm gonna print a period
after the variable.
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Now I need to
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create the condition that will end my
loop.
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So I'm gonna say, if my var is equal to
let's say eight, then go ahead and break.
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And that will stop the loop.
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Now we're using the console time up here,
we need to also end our timer.
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So we have a timer that starts.
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Now we need to create the corresponding
end timer.
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So I'm gonna say timeEnd.
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And,
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going to say loop.
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Cuz we want that to be titled exactly the
same there.
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And then I'm gonna go ahead and hit Enter.
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Now the my log test function has been
created
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and we can go ahead and call it and
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you'll notice that it even auto completes
for us
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because it knows that function is
available to us.
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So if I were to type in 1 and pass it that
value,
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it will print out every time the loop
runs.
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And then it will say, huh, that loop took
0.782 milliseconds to run.
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So that's a pretty fast loop.
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If I were to type in a value of seven,
we'll see that it actually takes less time
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to run, because it's looping zero times.
It only had to loop twice or once
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to actually get up to the value of eight
there.
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You notice down here that we can go ahead
and filter by errors.
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So, I had some errors earlier and we can
go ahead and look those,
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can also look at warnings which are
similar to errors, any kind of logs.
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So we created some logs earlier.
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And we can also go into debug mode there.
That is just a really small taste
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of what you can do with the console.
The console is incredibly robust, and
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if you wanna see more, definitely be sure
to check out the console API reference.
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