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Convert character to ASCII code in JavaScript

How can I convert a character to its ASCII code using JavaScript?

For example:

get 10 from "\n".

Answer*

"\n".charCodeAt(0);

Here is the documentation for [`charCodeAt`][1]:

> The `charCodeAt()` method returns an integer between 0 and 65535 representing the UTF-16 code unit at the given index.
>
> The UTF-16 code unit matches the Unicode code point for code points which can be represented in a single UTF-16 code unit. If the Unicode code point cannot be represented in a single UTF-16 code unit (because its value is greater than `0xFFFF`) then the code unit returned will be the first part of a surrogate pair for the code point. If you want the entire code point value, use `codePointAt()`. 

If you need to support non-BMP Unicode characters like U+1F602 😂, then don't use `charCodeAt`, as it will not return 128514 (or 0x1f602 in hexadecimal), it will give a result you don't expect:





 console.log("\u{1f602}".charCodeAt(0));
 // prints 55357 , which is 0xd83d in hexadecimal



 [1]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/charCodeAt

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821

The opposite of this is String.fromCharCode(10).

viam0Zah
– viam0Zah

2011年05月01日 09:38:22 +00:00
Commented May 1, 2011 at 9:38
227

Fun fact: you don’t really need the 0 (first argument value) — just "\n".charCodeAt() will do.

Mathias Bynens
– Mathias Bynens

2011年10月17日 09:40:29 +00:00
Commented Oct 17, 2011 at 9:40
54

@MathiasBynens: and fortunately this is documented: developer.mozilla.org/en/JavaScript/Reference/Global_Objects/…. "if it is not a number, it defaults to 0"

tokland
– tokland

2011年11月15日 19:46:40 +00:00
Commented Nov 15, 2011 at 19:46
14

You should point out that unlike String.fromCharCode( asciiNumVal ), stringInstance.charCodeAt( index ) is not a static method of class String

bobobobo
– bobobobo

2012年09月12日 19:09:06 +00:00
Commented Sep 12, 2012 at 19:09
29

@Mathias Bynens, It certainly does default to zero but I just ran a just out of interest test on performance and it performs **relatively badly compared using 0. jsperf.com/default-to-0-vs-0/4 ** Its a relative difference only, either way its very very quick.

wade montague
– wade montague

2013年05月09日 12:35:17 +00:00
Commented May 9, 2013 at 12:35

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Convert character to ASCII code in JavaScript

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