字符串

Reflect.ownKeys(String.prototype)
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// 部分不重要的做了删减
[
   
    "anchor",
    "at",
    "big",
    "blink",
    "bold",
    "charAt",
    "charCodeAt",
    "codePointAt",
    "concat",
    "endsWith",
    "fontcolor",
    "fontsize",
    "fixed",
    "includes",
    "indexOf",
    "italics",
    "lastIndexOf",
    "link",
    "localeCompare",
    "match",
    "matchAll",
    "normalize",
    "padEnd",
    "padStart",
    "repeat",
    "replace",
    "replaceAll",
    "search",
    "slice",
    "small",
    "split",
    "strike",
    "sub",
    "substr",
    "substring",
    "sup",
    "startsWith",
    "toString",
    "trim",
    "trimStart",
    "trimLeft",
    "trimEnd",
    "trimRight",
    "toLocaleLowerCase",
    "toLocaleUpperCase",
    "toLowerCase",
    "toUpperCase",
    "valueOf"
]
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var str = 'helloworld45zanlan'
console.log(str.endsWith('zanlan'));// true
console.log(str.startsWith('helloworld')); // true
console.log(str.includes('45')); // true
console.log('zanlan-'.repeat(3));// 'zanlan-zanlan-zanlan-'
console.log(/hell/.test(str)) // true
console.log(str.length)//18

'aAcd'.charCode.At(1) // 65
'aAcd'.charCode.At(0) // 97
String.fromCharCode(65)// "A"
String.fromCharCode(97)// "a"
'aAcd'.toLowerCase() // 'aacd'
'aAcd'.toUpperCase() // 'AACD'
'123456789'.substr(1,3) // "234"  截取长度为3
'123456789'.substring(1,3) // "23"
'123456789'.slice(1,3) // '23'
'123456789'.slice(-3,-1) // '78'
'123456789'.slice(-3) // '789'
'123456789'.substr(-3) // '789'
'123456789'.slice(30) // ''
'123456789'.substr(30) // ''

var str = "The full name of China is the People's Republic of China.";
console.log(str.indexOf("China")) // 17
console.log(str.indexOf("China",18)) // 51    18 ~ 终止位置56， 范围内找
console.log(str.lastIndexOf("China")) // 51
console.log(str.lastIndexOf("China"),50) // 17     50 ~ 起始位置0 范围内找
console.log(str.indexOf("America")) // -1
console.log(str.lastIndexOf("America")) // -1
console.log(str.search("China")) // 17  和indexOf功能一样，但是不能设置第二个参数
console.log(str.replace('is','yes')) // "The full name of China yes the People's Republic of China.";
console.log(str.replace(/china/gi,'China-China')) // The full name of China-China is the People's Republic of China-China.;
" Hello World!   ";
console.log(" Hello World!   ".trim())

var str = "HELLO WORLD";
str[0] = "A"; // 只读的，不产生错误，但不会工作
console.log(str[0])// 返回 H
console.log(str[30]) // undefined
console.log(str.charAt(30)) // ""
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数组

Reflect.ownKeys(Array.prototype)
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[
    "length",
    "constructor",
    "at",
    "concat",
    "copyWithin",
    "fill",
    "find",
    "findIndex",
    "lastIndexOf",
    "pop",
    "push",
    "reverse",
    "shift",
    "unshift",
    "slice",
    "sort",
    "splice",
    "includes",
    "indexOf",
    "join",
    "keys",
    "entries",
    "values",
    "forEach",
    "filter",
    "flat",
    "flatMap",
    "map",
    "every",
    "some",
    "reduce",
    "reduceRight",
    "toLocaleString",
    "toString",
    "findLast",
    "findLastIndex",
    null,
    null
]
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对象

Reflect.ownKeys(Object.prototype)
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[
    "constructor",
    "__defineGetter__",
    "__defineSetter__",
    "hasOwnProperty",
    "__lookupGetter__",
    "__lookupSetter__",
    "isPrototypeOf",
    "propertyIsEnumerable",
    "toString",
    "valueOf",
    "__proto__",
    "toLocaleString"
]
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函数

Reflect.ownKeys(Function.prototype)
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[
    "length",
    "name",
    "arguments",
    "caller",
    "constructor",
    "apply",
    "bind",
    "call",
    "toString",
    null
]
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统计字符串出现的次数，按权重排序
字符统计

var brr = "aaddccdc".split("");
var map = new Map();
brr.forEach((item) => {
    map.set(item, (map.get(item) || 0) + 1);
});
var arr = Array.from(map)
arr.sort(function (a, b) {
    if (a[1] - b[1] == 0) {
        return a[0].charCodeAt(0) - b[0].charCodeAt(0)
    }
    return b[1] - a[1]
})
var result = arr.reduce(function (res, item) {
    return res += item[0]
}, '')
console.log(result) // "cda"
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