A polyfill for `String.prototype.codePointAt`

codepointat.js

String.prototype.codePointAt || (String.prototype.codePointAt = function(index) {
    var code = this.charCodeAt(index);
    if (code >= 0xd800 && code <= 0xdbff) {
        var surr = this.charCodeAt(index + 1);
        if (surr >= 0xdc00 && surr <= 0xdfff)
            code = 0x10000 + ((code - 0xd800) << 10) + (surr - 0xdc00);
    }
    
    return code;
});