Internet Explorer, Closure Compiler and Trailing Commas

Question

I'm using html5boilerplate build script and when minifying the scripts (which uses Google Closure Compiler)

I'm getting this error

-js.all.minify:
     [echo] Minifying scripts
     [copy] Copying 3 files to /Users/Username/Desktop/Web/intermediate/js
    [apply] /Users/Juan/Desktop/Web/js/plugins.js:117: ERROR - Parse error. Internet Explorer has a non-standard intepretation of trailing commas. Arrays will have the wrong length and objects will not parse at all.
    [apply]                 }, { duration: 727 })
    [apply] 

             ^

But the code DOES work in IE 8 if run uncompiled.

This is the code

anim1.animate({
                    'left': '+=32px',
                    'filter': 'alpha(opacity=100)',
                    '-moz-opacity': '1',
                    '-khtml-opacity': '1',
                    'opacity': '1',
                }, { duration: 727 })

How can I make this code pass Compulsure Compiler?

Thanks

score 10 · Accepted Answer · answered Aug 06 '12 at 06:03

10

Remove the superfluous last comma from your object literal:

anim1.animate({
    'left': '+=32px',
    'filter': 'alpha(opacity=100)',
    '-moz-opacity': '1',
    '-khtml-opacity': '1',
    'opacity': '1'      // <-- No comma here.
}, { duration: 727 });  // <-- I'd also suggest a semicolon there.

As the Closure compiler says, literals with such trailing commas cannot be parsed by some browsers.

answered Aug 06 '12 at 06:03

Frédéric Hamidi

258,201
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I spend so much on this code I could not see it right in forn of my eyes. I still find it weird that the code works fine in IE 7,8,9 but the compiler treats it some kind of fatal error. Thanks Frédéric. – Juan Ignacio Aug 06 '12 at 11:55
1

Here's an article that explains why: http://www.enterprisedojo.com/2010/12/19/beware-the-trailing-comma-of-death/. You can convert this error to a warning by using the `--jscomp_warning internetExplorerChecks` flag. – Chad Killingsworth Aug 06 '12 at 15:43
It would have been really nice to have JSHint and JSLint tell me this, as I have just wasted all day on this... SMDH Thanks – Erik Grosskurth Dec 16 '13 at 18:44

score 4 · Answer 2 · answered Aug 06 '12 at 18:01

4

Or enable EcmaScript 5 mode. Ecmascript 5 does standardize the trailing comma behavior but IE8 does not fully support it ES5 (neither does IE9 which is missing strict mode).

answered Aug 06 '12 at 18:01

John

5,443
15
21

Internet Explorer, Closure Compiler and Trailing Commas

2 Answers2

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