Sort JavaScript array of strings with custom sorting for punctuation in first character

This is a bit trickier that it may seem at first. But here is one way to do it, assuming the special characters listed are the only ones you're concerned with:

var separator = '\uFFFF';

var prefixes = {
    '~': '1',
    '&': '2',
    '@': '3',
    '%': '4',
    '+': '5'
};

function specialsort( array ) {
    var prefixed = array.map( function( value ) {
        var prefix = prefixes[ value.charAt(0) ] || '9';
        return prefix +
            value.toLowerCase() +
            separator + value;
    });
    prefixed.sort();
    return prefixed.map( function( value ) {
        return value.split(separator)[1];
    });
}

var nicks = [ "~xxx", "@blue", "&demo", "+voice", "%yyy", "nick1", "Nick2", "webmaster" ];

var sorted = specialsort( nicks );
console.log( sorted );

The code works by creating a new array with strings formatted like this:

1. The first character is a digit 1-5 for the special characters or 9 for any other character found at the beginning of each string. (You could extend this to two digits using '01', '02', etc. and '99' for other characters.)
2. Next is the string in lowercase.
3. Then a Unicode character with a very large value (\uFFFF) as a separator.
4. Finally, the original string.

The array of these strings can then be sorted directly, and the result is converted to a new array by splitting the strings on that separator and using the part after the separator (the original string).

Or, a slightly simpler approach using a sort callback function:

var prefixes = {
    '~': '1',
    '&': '2',
    '@': '3',
    '%': '4',
    '+': '5'
};

function specialsort( array ) {
    return array.sort( function( a, b ) {
        a = ( prefixes[ a.charAt(0) ] || '9' ) + a.toLowerCase();
        b = ( prefixes[ b.charAt(0) ] || '9' ) + b.toLowerCase();
        return a < b ? -1 : a > b ? 1 : 0;
    });
}

var nicks = [ "~xxx", "@blue", "&demo", "+voice", "%yyy", "nick1", "Nick2", "webmaster" ];

var sorted = specialsort( nicks );
console.log( sorted );

For lengthy arrays, I tend to go for the first approach—making a modified array and sorting it—because it can be faster than using a sort callback. But the sort callback is a bit simpler and there's nothing wrong with it for an array of this size.

The sort callback approach does have one other advantage over the modified array: it doesn't depend on that slightly hacky separator character.

Either way, the output is:

["~xxx", "&demo", "@blue", "%yyy", "+voice", "nick1", "Nick2", "webmaster"]

Here's a fiddle for the first version and a fiddle for the second version.