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40 lines
1.9 KiB
Markdown
40 lines
1.9 KiB
Markdown
---
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title: Semicolons
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---
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Semicolons are not required in JavaScript. This is because JavaScript has a feature called "Automatic Semicolon Insertion" or ASI for short. ASI puts semicolons in your JavaScript for you. It is always active by default and it's a part of the language and can not be disabled.
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ASI has a set of rules it uses to determine where it should insert semicolons. If there is already a semicolon in place, it won't change anything. See <a href='http://stackoverflow.com/a/2846298/3467946' target='_blank' rel='nofollow'>this StackOverflow answer</a> for more information on how ASI works.
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There is only one case where ASI fails: when a line starts with an opening bracket `(`. To avoid this causing errors, when a line starts with an opening bracket, you can put a semicolon at the beginning of the line that has the opening bracket:
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```js
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;(function() {
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console.log('Hi!')
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})
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```
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Note that this is only required if you don't use semicolons.
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A consistent coding style makes code more readable. Decide whether you will or won't use semicolons, and do so everywhere.
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## Errors you might run into
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When JavaScript was first made it was meant to aid beginners to get into programming. Nobody wants to be searching for a dang semi-colon in their code when they first start programming. So the choice of semi-colons was implemented, as stated above they are technically there.
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For example:
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```js
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function foo(x) {
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return
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function(y) {
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return x + y;
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}
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}
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let z = foo(10);
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z(10)// TypeError z is not a function
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// Because of Automatic Semicolon Insertion, our inner function does not exist.
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```
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JavaScript will implement semi-colons where they are expected.
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### Other resources
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<a href='http://blog.izs.me/post/2353458699/an-open-letter-to-javascript-leaders-regarding' target='_blank' rel='nofollow'>An Open Letter to JavaScript Leaders Regarding Semicolons</a>
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