更好的Unicode支持
- 一直基于16位字符編碼（UTF-16）
- 基本多文種平面（BMP）
let text = "??"
console.log(text.length)//2
console.log(/^.$/.test(text))//false
console.log(text.charAt(0));//""不表示任何可打印的字符
console.log(text.charAt(1));//""
console.log(text.charCodeAt(0));//55362 每個(gè)166位編碼單元對(duì)應(yīng)的數(shù)值
console.log(text.charCodeAt(1));//57271
//非BMP字符 返回不同
let text = "??a"
console.log(text.charCodeAt(0));//55362
console.log(text.charCodeAt(1));//57271
console.log(text.charCodeAt(2));//97
console.log(text.codePointAt(0))//134071
console.log(text.codePointAt(1))//57271
console.log(text.codePointAt(2))//97
function is32Bit(c) {
return c.codePointAt(0) > 0xFFFF;
}
console.log(is32Bit("??")) //true
console.log(is32Bit("a")) //false
console.log(String.fromCodePoint(134071));//"??" fromCharCode
let normalized = values.map(function(){
return text.normalize();
})
normalized.sort(function(first, second){
if(first < second){
return -1;
} else if (first === second) {
return 0;
} else {
return 1;
}
})
//
values.sort(function(first, second){
let firstNormalized = first.normalized();
let secondNormalized = second.normalized();
if(firstNormalized < secondNormalized) {
return -1;
} else if(firstNormalized === secondNormalized){
return 0;
} else {
return 1
}
})
//
values.sort(function(first, second){
let firstNormalized = first.normalized("NFD");
let secondNormalized = second.normalized("NFD");
if(firstNormalized < secondNormalized) {
return -1;
} else if(firstNormalized === secondNormalized){
return 0;
} else {
return 1
}
})
//
let text = "??"
console.log(text.length);//2
console.log(/^.$/.test(text));//false
console.log(/^.$/u.test(text));//true
//效率低
function codePointLength(text){
let result = text.match(/[\s\S]/gu);
return result?result.length:0;
}
console.log(codePointLength("abc"));//3
console.log(codePointLength("??bc"));
//老式Javascript引擎中
function hasRegExp() {
try {
var pattern = new RegExp(".","u");
return true;
} catch(ex) {
return false;
}
}
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