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脚本之家网站的支持！
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