Javascript Array delete or pop causing race condition with console.log?

Question

On the current Google Chrome (Version 22.0.1229.79, on an iMac with Mountain Lion), the following code

var arr = [1, 3, 5];
console.log(arr);

delete arr[1];
console.log(arr);

console.log(arr.pop());
console.log(arr);

will show

[1, undefined × 2] 
[1, undefined × 2] 
5 
[1, undefined × 1]

there are also other situation that caused Firefox to behave similarly as well. Are they bugs on Chrome and Firefox -- but it would seem strange that both Firefox and Chrome are susceptible to similar bugs -- or is it some behavior with array delete and console.log? Supposedly, console.log should not be running on a separate thread.

possible duplicate of [Is Chrome's JavaScript console lazy about evaluating arrays?](http://stackoverflow.com/questions/4057440/is-chromes-javascript-console-lazy-about-evaluating-arrays) — Felix Kling, Oct 07 '12 at 09:13
@動靜能量: Seems like a bug that was done by the same person. FF14 is fine, while FF15 is not. Vandalized? — Jay, Oct 07 '12 at 09:29

score 1 · Answer 1 · answered Oct 07 '12 at 08:16

1

In Firefox 7.0:

var arr = [1,3,5];

console.log(delete arr[1]); // will show [1, undefined, 5]

And in my opinion it's a correct behavior =) So may be it's just a bug.

answered Oct 07 '12 at 08:16

XiM

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The op is not asking why the result is `[1, undefined, 5]`. – xdazz Oct 07 '12 at 08:19
a similar bug showed up on Firefox 15.0.1 but it involved 10 tests for `arr1` to `arr10`, and if I removed the test for `arr9`, then the output became "correct", and if I removed the test for `arr1` to `arr8`, the output became "correct" again. `arr10` is totally independent of other array tests, so it is similar to what Chrome was showing in the original question – nonopolarity Oct 07 '12 at 08:20
So `delete` is working correct and `console.log` isn't. If you do not re-define the `console.log`, I would suggest that this is simply a bug of browsers. – XiM Oct 07 '12 at 08:44

score 1 · Accepted Answer · edited May 23 '17 at 10:24

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It is due to queued up console.log processing, so the printing is delayed, and it shows a later version of the object or array: Is Chrome's JavaScript console lazy about evaluating arrays?

My answer there has 5 solutions and JSON.stringify() was the best one.

edited May 23 '17 at 10:24

Community

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answered Oct 09 '12 at 16:06

nonopolarity

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Javascript Array delete or pop causing race condition with console.log?

2 Answers2