js byte[] 和string 相互转换 UTF-8

from:http://blog.csdn.net/u013022210/article/details/55101558

function stringToByte(str) {  
    var bytes = new Array();  
    var len, c;  
    len = str.length;  
    for(var i = 0; i < len; i++) {  
        c = str.charCodeAt(i);  
        if(c >= 0x010000 && c <= 0x10FFFF) {  
            bytes.push(((c >> 18) & 0x07) | 0xF0);  
            bytes.push(((c >> 12) & 0x3F) | 0x80);  
            bytes.push(((c >> 6) & 0x3F) | 0x80);  
            bytes.push((c & 0x3F) | 0x80);  
        } else if(c >= 0x000800 && c <= 0x00FFFF) {  
            bytes.push(((c >> 12) & 0x0F) | 0xE0);  
            bytes.push(((c >> 6) & 0x3F) | 0x80);  
            bytes.push((c & 0x3F) | 0x80);  
        } else if(c >= 0x000080 && c <= 0x0007FF) {  
            bytes.push(((c >> 6) & 0x1F) | 0xC0);  
            bytes.push((c & 0x3F) | 0x80);  
        } else {  
            bytes.push(c & 0xFF);  
        }  
    }  
    return bytes;  


}  


 function byteToString(arr) {  
    if(typeof arr === 'string') {  
        return arr;  
    }  
    var str = '',  
        _arr = arr;  
    for(var i = 0; i < _arr.length; i++) {  
        var one = _arr[i].toString(2),  
            v = one.match(/^1+?(?=0)/);  
        if(v && one.length == 8) {  
            var bytesLength = v[0].length;  
            var store = _arr[i].toString(2).slice(7 - bytesLength);  
            for(var st = 1; st < bytesLength; st++) {  
                store += _arr[st + i].toString(2).slice(2);  
            }  
            str += String.fromCharCode(parseInt(store, 2));  
            i += bytesLength - 1;  
        } else {  
            str += String.fromCharCode(_arr[i]);  
        }  
    }  
    return str;  
}