Understading for loop in Javascript

Question

Yesterday i have started courses on W3Schools. I am a little confused about one for loop in JavaScript.

var text = "";
var i;
for (i = 0; i < 5; i++) {
    text += "The number is " + i + "<br>";
}

It gives the following output:

The number is 0

The number is 1

The number is 2

The number is 3

The number is 4

What I am little confused is:

The text value it's updated with every iteration, so, after first iteration:

The number is 0

As text = The number is 0

Then are the next ones, and I can't understand why it prints out "the number is 1" and so on, instead of

The number is 0 The number is 1

The number is 0 The number is 1 The number is 2

The number is 0 The number is 1 The number is 2 The number is 3

The number is 0 The number is 1 The number is 2 The number is 3 The number is 4

As with every next iteration the var text is updated and the for loop doesn't quit for loop to reset the value to var text = ""

The code you posted does not have any "output" at all. It just accumulates strings. What happens with text after that loop? — Pointy
– Pointy, Commented Dec 30, 2015 at 14:21
document.getElementById("demo").innerHTML = text; It is this task from linkW3schools //EDIT - doesn't matter anyways, I understood now :) :) — user5730872
– user5730872, Commented Dec 30, 2015 at 14:26
It's because of the + in text +=, it means "add to the previous value", remove it and text's value will be overwritten by new content each iteration. — Shanoor
– Shanoor, Commented Dec 30, 2015 at 14:28

lleaff · Accepted Answer · 2015-12-30 14:23:42Z

1

That's because you accumulate the text inside a variable and then at the end print it.

If you watch the evolution of the text variable using a debugger you would see what you describe at the end.

answered Dec 30, 2015 at 14:23

lleaff

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