js实现unicode码字符串与utf8字节数据互转详解
js的string变量存储字符串使用的是unicode编码，要保存时必须选择其他编码后进行传输，比如转成utf-8,utf-32等。存储到数据库中为utf-8编码，读取出来如何转换成正确的字符串就成了问题。现在给出解决方案，可以正确支持中文、emoji表情、英文混合的字符串编码互转。
/**
* Created by hdwang on 2019/1/28.
*/
var convertUtf8 = (function() {
/**
* unicode string to utf-8
* @param text 字符串
* @returns {*} utf-8编码
*/
function toBytes(text) {
var result = [], i = 0;
text = encodeURI(text);
while (i < text.length) {
var c = text.charCodeAt(i++);
// if it is a % sign, encode the following 2 bytes as a hex value
if (c === 37) {
result.push(parseInt(text.substr(i, 2), 16))
i += 2;
// otherwise, just the actual byte
} else {
result.push(c)
}
}
return coerceArray(result);
}
/**
* utf8 byte to unicode string
* @param utf8Bytes
* @returns {string}
*/
function utf8ByteToUnicodeStr(utf8Bytes){
var unicodeStr ="";
for (var pos = 0; pos < utf8Bytes.length;){
var flag= utf8Bytes[pos];
var unicode = 0 ;
if ((flag >>>7) === 0 ) {
unicodeStr+= String.fromCharCode(utf8Bytes[pos]);
pos += 1;
} else if ((flag &0xFC) === 0xFC ){
unicode = (utf8Bytes[pos] & 0x3) << 30;
unicode |= (utf8Bytes[pos+1] & 0x3F) << 24;
unicode |= (utf8Bytes[pos+2] & 0x3F) << 18;
unicode |= (utf8Bytes[pos+3] & 0x3F) << 12;
unicode |= (utf8Bytes[pos+4] & 0x3F) << 6;
unicode |= (utf8Bytes[pos+5] & 0x3F);
unicodeStr+= String.fromCodePoint(unicode) ;
pos += 6;
}else if ((flag &0xF8) === 0xF8 ){
unicode = (utf8Bytes[pos] & 0x7) << 24;
unicode |= (utf8Bytes[pos+1] & 0x3F) << 18;
unicode |= (utf8Bytes[pos+2] & 0x3F) << 12;
unicode |= (utf8Bytes[pos+3] & 0x3F) << 6;
unicode |= (utf8Bytes[pos+4] & 0x3F);
unicodeStr+= String.fromCodePoint(unicode) ;
pos += 5;
} else if ((flag &0xF0) === 0xF0 ){
unicode = (utf8Bytes[pos] & 0xF) << 18;
unicode |= (utf8Bytes[pos+1] & 0x3F) << 12;
unicode |= (utf8Bytes[pos+2] & 0x3F) << 6;
unicode |= (utf8Bytes[pos+3] & 0x3F);
unicodeStr+= String.fromCodePoint(unicode) ;
pos += 4;
} else if ((flag &0xE0) === 0xE0 ){
unicode = (utf8Bytes[pos] & 0x1F) << 12;;
unicode |= (utf8Bytes[pos+1] & 0x3F) << 6;
unicode |= (utf8Bytes[pos+2] & 0x3F);
unicodeStr+= String.fromCharCode(unicode) ;
pos += 3;
} else if ((flag &0xC0) === 0xC0 ){ //110
unicode = (utf8Bytes[pos] & 0x3F) << 6;
unicode |= (utf8Bytes[pos+1] & 0x3F);
unicodeStr+= String.fromCharCode(unicode) ;
pos += 2;
} else{
unicodeStr+= String.fromCharCode(utf8Bytes[pos]);
pos += 1;
}
}
return unicodeStr;
}
function checkInt(value) {
return (parseInt(value) === value);
}
function checkInts(arrayish) {
if (!checkInt(arrayish.length)) { return false; }
for (var i = 0; i < arrayish.length; i++) {
if (!checkInt(arrayish[i]) || arrayish[i] < 0 || arrayish[i] > 255) {
return false;
}
}
return true;
}
function coerceArray(arg, copy) {
// ArrayBuffer view
if (arg.buffer && arg.name === 'Uint8Array') {
if (copy) {
if (arg.slice) {
arg = arg.slice();
} else {
arg = Array.prototype.slice.call(arg);
}
}
return arg;
}
// It's an array; check it is a valid representation of a byte
if (Array.isArray(arg)) {
if (!checkInts(arg)) {
throw new Error('Array contains invalid value: ' + arg);
}
return new Uint8Array(arg);
}
// Something else, but behaves like an array (maybe a Buffer? Arguments?)
if (checkInt(arg.length) && checkInts(arg)) {
return new Uint8Array(arg);
}
throw new Error('unsupported array-like object');
}
return {
toBytes: toBytes,
fromBytes: utf8ByteToUnicodeStr
}
})()
针对emoji的字节字符，占两个unicode字符。使用String.fromCharCode也可以实现，需要进行两次fromCharCode，没有fromPointCode方便。下面展示了utf-8的4字节转换为unicode(utf-16)的过程。
//高char10位[一个unicode字符] (2+6+2=10)
unicode = ((utf8Bytes[pos] & 0x3)) << 8 |((utf8Bytes[pos+1] & 0x3f) << 2) |((utf8Bytes[pos+2] >> 4) & 0x03);
//减去1F600中的1，这里减去6个0即可，低位char已经占据10位
unicode = unicode - parseInt('1000000',2)
//加上utf-16高char的标识符
unicode = 0xD800 + unicode;
console.log(unicode);
unicodeStr += String.fromCharCode(unicode);
//低char10位[一个unicode字符](4+6)
unicode = ((utf8Bytes[pos+2] & 0x0F) << 6) | (utf8Bytes[pos+3] & 0x3F);
//加上utf-16低char的标识符
unicode = 0xDC00 + unicode;
console.log(unicode);
unicodeStr+= String.fromCharCode(unicode);
pos += 4;
以上所述是小编给大家介绍的js实现unicode码字符串与utf8字节数据互转详解整合，希望对大家有所帮助，如果大家有任何疑问请给我留言，小编会及时回复大家的。在此也非常感谢大家对网站的支持！
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