Usage of compound conditional statements within JavaScript for loop

Question

Can you use a compound conditional statement in a JavaScript for loop?

Here is an example,

//using a compound conditional statement
//within a for loop, JavaScript
for (var i=0; i < res.length && i < 5; i++) {};

//or
for (var i=0; i < res.length || i < 5; i++) {};

Is the fact that your second example might run infinitely an example of such a logic error or just serendipitous irony? — Wiseguy
– Wiseguy, Commented Jun 3, 2012 at 22:55
It's a logic statement like any other; any errors will be PEBKAC. — Dave Newton
– Dave Newton, Commented Jun 3, 2012 at 22:56
@Niko—I think you mean "yes", the question has been edited. — RobG
– RobG, Commented Jun 4, 2012 at 2:51

Esailija · Accepted Answer · 2012-06-03 23:00:49Z

1

Yes it could lead to a logic error -- like any other code. Hopefully you test your code so you can find those errors and fix them.

answered Jun 3, 2012 at 23:00

Esailija

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Comments

Ed Heal · Accepted Answer · 2012-06-03 23:00:45Z

0

Brent - The two statements are not the same. You are trying to use De Morgan's laws. hence the second statement should read

for (var i=0; i >= res.length || i >= 5; i++) {};

It would be better to do this

var end = res.length < 5 ? res.length : 5;

for (var i=0; i < end; ++i) {}

This will reduce the overhead or doing the logic of working out when to terminate the loop.

answered Jun 3, 2012 at 23:00

Ed Heal

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