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1.10 Converting Between Unicode Values and String Characters

NN 2, IE 3

1.10.1 Problem

You want to obtain the Unicode code number for an alphanumeric character or vice versa.

1.10.2 Solution

To obtain the Unicode value of a character of a string, use the charCodeAt( ) method of the string value. A single parameter is an integer pointing to the zero-based position of the character within the string:

var code = myString.charCodeAt(3);

If the string consists of only one character, use the 0 argument to get the code for that one character:

var oneChar = myString.substring(12, 13);
var code = oneChar.charCodeAt(0);

The returned value is an integer.

To convert an Unicode code number to a character, use the fromCharCode( ) method of the static String object:

var char = String.fromCharCode(66);

Unlike most string methods, this one must be invoked only from the String object and not from a string value.

1.10.3 Discussion

ASCII values and Unicode values are the same for the basic Latin alphanumeric (low-ASCII) values. But even though Unicode encompasses characters from many written languages around the world, do not expect to see characters from other writing systems displayed in alert boxes, text boxes, or rendered pages simply because you know the Unicode values for those characters; the browser and operating system must be equipped for the language encompassed by the characters. If the character sets are not available, the characters generated by such codes will be question marks or other symbols. A typical North American computer won't know how to produce a Chinese character on the screen unless the target writing system and font sets are installed for the OS and browser.

1.10.4 See Also

Recipe 1.2 for other ways to extract single-character substrings.

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