Assignment in while loop - Javascript

Question

I have strange situation - here is Javascript code - and in NetBeans IDE 8.0 I see an alert "Expected a conditional expression and instead saw an assignment":

var elem;
var a = 0;
while ((elem = document.getElementById('id-' + a)) !== null) {
    //Some code
    a++;
}

But code works fine. Maybe this is some bug in Netbeans IDE 8.0?

score 8 · Answer 1 · answered Jan 23 '15 at 10:55

8

The code is fine. The IDE's warning is because usually a comparison (==) is made, but sometimes an assignment (=) is what is actually wanted. It's to catch mistakes made by missing an equals sign.

Here, you set the elem variable, and at the same time, compare it to null.

answered Jan 23 '15 at 10:55

Scimonster

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Also worth noting that the null check is redundant with `getElementById`, it's just there for the benefit of the reader – blgt Jan 23 '15 at 10:57
If I use `!=` then I get additional warning: Expected "!==" and instead saw "!=" – Ernestas Gruodis Jan 23 '15 at 10:58
@ErnestasGruodis I guess it's being very strict about what is allowed. `!=` is valid. – Scimonster Jan 23 '15 at 10:59

Assignment in while loop - Javascript

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