Expected an assignment or function call and instead saw an expression

Question

I'm totally cool with this JSLint error. How can I tolerate it? Is there a flag or checkbox for it?

You get it when you do stuff like:

v && arr.push(v);

as opposed to:

if (v) {
    arr.push(v);
}

Both do the same exact thing. If you put:

window.test = function(v) {
    'use strict';
    var arr = [];
    if (v) {
        arr.push(v);
    }
    return arr;
};

into the minifier it minifies down to this anyway:

window.test=function(a){var b=[];a&&b.push(a);return b};

score 76 · Accepted Answer · answered Mar 02 '12 at 13:30

76

I don't think JSLint has an option to turn that off.

JSHint (a fork with more options) has an option for it, though: The expr option, documented as "if ExpressionStatement should be allowed as Programs".

answered Mar 02 '12 at 13:30

T.J. Crowder

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@diEcho: You can also download and use it locally (that's what I do). I run it via NodeJS with my preferred options set, *dramatically* helps my confidence in correct code. :-) – T.J. Crowder Mar 02 '12 at 13:35
Can describe more please, why that warning happened? – Mohammad Kermani Oct 04 '16 at 10:36

score 37 · Answer 2 · edited May 03 '23 at 00:19

37

You can add the following line to ignore that warning:

/*jshint -W030 */

You can read more about it here.

edited May 03 '23 at 00:19

Henry Ecker

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answered May 28 '14 at 15:59

ReedD

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The answer is completely unrelated to the question, which was about JSLint, not JSHint. – Arseni Mourzenko Feb 02 '15 at 19:28
15

Yet its still the most useful answer for the majority of people who land here. – Charlie Martin Mar 18 '15 at 21:01
2

"completely unrelated"? Because JSHint is completely unrelated to JSLint? – iconoclast Dec 17 '15 at 23:17

Shivam · Answer 3 · 2020-04-08T20:16:22.420

11

People who are looking how to suppress it when using ESLint. You can ingnore it by writing the following comment just above the line no-unused-expressions

// eslint-disable-next-line no-unused-expressions

You can also suppress the warning for the entire file by placing the following comment at the very top of the file

/* eslint-disable no-unused-expressions */

edited Apr 08 '20 at 20:16

answered Dec 17 '18 at 06:01

Shivam

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I recommend you to also provide the link of the documentation of this specific rule [no-unused-expressions](https://eslint.org/docs/rules/no-unused-expressions#top) – johannchopin Apr 08 '20 at 14:41

KooiInc · Answer 4 · 2012-03-02T13:51:34.807

9

There's no option for this in JSLint. You can circumvent it using:

var dummy = v && arr.push(v);

NB: dummy evaluates to true after that.

Another workaround could be:

function expression(statement) { 
 'use strict';
 return statement; 
}
expression(v && arr.push);

edited Mar 02 '12 at 13:51

answered Mar 02 '12 at 13:31

KooiInc

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It'll work but it's silly. The minifier will actually sort that out and but for readability it'd be better to just use the `if` statement than that IMO. – ryanve Mar 02 '12 at 13:50
That's true. But you asked for a way to tolerate is. Added another workaround. It's like Crockford said somewhere: *jsLint is designed to be a pain in the ass for programmers* ;~) – KooiInc Mar 02 '12 at 13:54
WRONG the wonderful && hack does not work in jsLint... maybe depends on version... – faebster Feb 12 '16 at 16:23

Expected an assignment or function call and instead saw an expression

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