js字符串转utf-8

function toUtf8(str) {   
    var out, i, len, c;   
    out = "";   
    len = str.length;   
    for(i = 0; i < len; i++) {   
        c = str.charCodeAt(i);   
        if ((c >= 0x0001) && (c <= 0x007F)) {   
            out += str.charAt(i);   
        } else if (c > 0x07FF) {   
            out += String.fromCharCode(0xE0 | ((c >> 12) & 0x0F));   
            out += String.fromCharCode(0x80 | ((c >>  6) & 0x3F));   
            out += String.fromCharCode(0x80 | ((c >>  0) & 0x3F));   
        } else {   
            out += String.fromCharCode(0xC0 | ((c >>  6) & 0x1F));   
            out += String.fromCharCode(0x80 | ((c >>  0) & 0x3F));   
        }   
    }   
    return out;   
}