Question

107

How to convert large UTF-8 strings into ASCII?

rated 0 times [ 108] [ 1] / answers: 1 / hits: 62752 / 15 Years ago, thu, may 7, 2009, 12:00:00

I need to convert large UTF-8 strings into ASCII. It should be reversible, and ideally a quick/lightweight algorithm.

How can I do this? I need the source code (using loops) or the JavaScript code. (should not be dependent on any platform/framework/library)

Edit: I understand that the ASCII representation will not look correct and would be larger (in terms of bytes) than its UTF-8 counterpart, since its an encoded form of the UTF-8 original.

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catrinas

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2 Years ago

answered 15 Years ago harleyterryp · Accepted Answer

You could use an ASCII-only version of Douglas Crockford's json2.js quote function. Which would look like this:

    var escapable = /[\\x00-x1fx7f-uffff]/g,

        meta = {    // table of character substitutions

            'b': '\b',

            't': '\t',

            'n': '\n',

            'f': '\f',

            'r': '\r',

            '' : '\',

            '\': '\\'

        };



    function quote(string) {



// If the string contains no control characters, no quote characters, and no

// backslash characters, then we can safely slap some quotes around it.

// Otherwise we must also replace the offending characters with safe escape

// sequences.



        escapable.lastIndex = 0;

        return escapable.test(string) ?

            '' + string.replace(escapable, function (a) {

                var c = meta[a];

                return typeof c === 'string' ? c :

                    '\u' + ('0000' + a.charCodeAt(0).toString(16)).slice(-4);

            }) + '' :

            '' + string + '';

    }

This will produce a valid ASCII-only, javascript-quoted of the input string

e.g. quote(Doppelgänger!) will be Doppelgu00e4nger!

To revert the encoding you can just eval the result

var encoded = quote(Doppelgänger!);

var back = JSON.parse(encoded); // eval(encoded);