; before document ready in jquery

Question

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What does the leading semicolon in JavaScript libraries do?

I am reading the jquery flexslider source code and i see a ; before the document ready call

;(function ($) {...

Can anyone tell me why we need a ; ?

you don't need the `;`. It's probably a typo. – zzzzBov Jan 22 '12 at 18:17 — zzzzBov, Jan 22 '12 at 18:17

score 5 · Answer 1 · answered Jan 22 '12 at 18:18

5

This is just to protect against any previous code lines that might be missing a semicolon.

If you know that the code before has a semicolon at the end, this semicolon is not needed at all.

answered Jan 22 '12 at 18:18

Guffa

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score 3 · Accepted Answer · answered Jan 22 '12 at 18:19

It's included in case...

the code gets grouped into the same file with other code, and
the other code didn't include a semicolon at the end.

For example...

    (function() {

       // some bundled plugin

    })()  // <--- no semicolon

//  v--- semicolon saved the day    
    ;(function ($) {

       // flexslider plugin

    })();

Without the semicolon, the () around the flexslider plugin would have been interpreted as a function call, and would have tried to call the return result of the previous function.

score 1 · Answer 3 · answered Jan 22 '12 at 18:19

1

This is not a typo. ; prevents javascript errors in compliled/minified/compressed files. For example when several independent libraries/plugins get compressed together.

answered Jan 22 '12 at 18:19

dfsq

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; before document ready in jquery

3 Answers3