写了个字符串的转码解码函数

function isString(variable) {
    return Object.prototype.toString.call(variable).indexOf(‘String‘) != -1;
}

function isNumeric(variable) {
    return !isNaN(parseFloat(variable)) && isFinite(variable);
}

function stringEncode(string) {
    string = isString(string) || isNumeric(string) ? String(string) : ‘‘;

    var code,
        i = 0,
        code_string = ‘‘,
        len = string.length;

    while(i < string.length) {
        code = string.charCodeAt(i);
        code_string += ‘‘ + String(code).length + code;
        i++;
    }

    return code_string;
}

function stringDecode(code) {
    var i = 0,
        code_len,
        decode_string = ‘‘;
    code = String(code);
    while(i < code.length) {
        code_len = +code.charAt(i);
        i++;
        decode_string += String.fromCharCode(+code.substr(i, code_len));
        i += code_len;
    }
    return decode_string;
}