实现String转bytes属性扩展

String.prototype.toBytes = function () {
     var ch, st, re = [];
     for (var i = 0; i < this.length; i++) {
         ch = this.charCodeAt(i);   // get char
         st = [];                   // set up "stack"
         do {
             st.push(ch & 0xFF);    // push byte to stack
             ch = ch >> 8;          // shift value down by 1 byte  
         }
         while (ch);
         // add stack contents to result  
         // done because chars have "wrong" endianness  
         re = re.concat(st.reverse());
     }
     // return an array of bytes  
     return re;
 }