Why does this javascript loop return infinitely?

Question

Can someone please explain to me why the following code returns an infinite loop rather than redefining foo?

var foo = 2;

while (foo = 2) {
   foo = 3;
}

console.log('foo is ' + foo);

Of course, the first time through the loop is going to run because foo indeed equals 2. However, I don't understand why to keeps running; after the first time through foo should now be set to 3, the parameter should return false, and console.log('foo is ' + foo); should print foo is 3.

Clearly I am missing something here.

what is that even supposed to do?

user1231232141214124
– user1231232141214124

2014-04-01 04:33:32 +00:00
Commented Apr 1, 2014 at 4:33 — user1231232141214124
– user1231232141214124, Commented Apr 1, 2014 at 4:33

Aashray · Accepted Answer · 2014-04-01 04:35:10Z

2

You are assigning the value 2 to foo instead of comparing it in the condition here:

while (foo = 2)

Change it to:

while (foo == 2)

answered Apr 1, 2014 at 4:35

Aashray

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TGH · Accepted Answer · 2014-04-01 04:34:04Z

2

while (foo == 2) {
   foo = 3;
}

You are missing an equal sign (or two if you want an even stricter check)

while (foo === 2) {
   foo = 3;
}

answered Apr 1, 2014 at 4:34

TGH

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2 Comments

Aashray Over a year ago

No syntactically it is completely correct. It's a logical error.

Scott Rippey Over a year ago

JavaScript has a concept of "truthy" and "falsey", which means that you can use boolean logic on non-boolean values. The value 2 is truthy, so while (2) is the same as while (true).

BAP · Accepted Answer · 2014-04-01 04:44:51Z

0

You may miss "while (foo == 2)" when open the loop,

if it again prints infinity let it know me..

answered Apr 1, 2014 at 4:44

BAP

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