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The return from a For loop

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Nov 04.2017

I’m not understanding why the code below returns the number 3, three times.

The piece of code

[CODE]for(var i=0; i<3; i++)[/CODE]

starts the value of i at 0. Then, it says as long as i is less than 3, the value increases by one. So, it seems to me the values of 1 and 2 would get passed to console.log(i) and then stop because it says i<3. What am I not undestanding?

Here’s the full program:

[CODE]
<!DOCTYPE html>
<html>
<body>

<p>

</p>

<script>
var a = [];
for(var i=0; i<3; i++) {
a[i] = function() { console.log(i) };
}

a[0]();
a[1]();
a[2]();
</script>

</body>
</html>

[/CODE]

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JavaScript

1 Comments(s) ↴

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@SempervivumNov 04.2017 — This is a common problem. For explanation and solutions read this:

http://www.webdeveloper.com/forum/showthread.php?363139-For-loop-not-working-help

Shortened:

After the loop is finished, the value of i is 3. Thus 3 is logged three times.

Solution:
for (var i = 0; i &lt; 3; i++) {
a[i] = function (idx) { return function() { console.log(idx) } }(i);
}

Alternative solution: use "let" instead of "var":
for (let i = 0; i &lt; 3; i++) {
a[i] = function () { console.log(i) };
}This is more easy and short but I'm not shure about browser support.
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