// 建立数组的四种形式: 字面上量, String(), new String() 前面三种是基本上正则表达式 前面是提及正则表达式
// 转化成为数组 1String() 2显式切换+”” 3`${}` 4toString()
let num1 = null;
// num1 = String(num1)
// num1 = `${num1}`
// num1 = new String(num1);
// console.log(typeof num1.valueOf(), num1.valueOf());
// num1 = String(num1);
num1 = `${num1}`
console.log(typeof num1);
console.log(num1.length);
// 常见形式
//charAt() 根据索引返回指定字符
let lstr = hello world!;
console.log(lstr.charAt(lstr.length – 1));
//concat() 连接成新数组 (可以多个),不改变原来数组
let lstr1 = myBaby;
let lstr2 = ,haha
let arr2 = [xixi, haha];
let arr3 = { name: zhangsan, age: 12 }
let arr = lstr1.concat(lstr, lstr2, arr2, arr3);
let arr4 = lstr1.concat(lstr, lstr2, …arr2, arr3);
console.log(arr, arr4);
// endsWith() 是否以某个数组结尾 startsWith()是否以某个数组开始
let str3 = this is my baby!;
let v = str3.endsWith(baby!);
let b = str3.startsWith(this);
console.log(v, b, str3.length);
// includes() 数组中是否包含指定数组，有返回true，没有返回false
let str4 = this mood is my;
let t = str4.includes(mood);
let t1 = str4.includes(tt);
let t2 = str4.includes( );
console.log(t, t1, t2);
// indexOf() 检索数组中是否存在某个数组，有返回指定索引，没有返回-1 从前查找
let str5 = Brave new world;
let index1 = str5.indexOf(new);
let index2 = str5.indexOf(haha);
console.log(index1, index2);
// lastIndexOf() 检索数组中是否存在某个数组，有返回指定索引，没有返回-1 从后查找
let str6 = “Blue Whale, Killer Whale”;
let index3 = str6.lastIndexOf(Whale);
let index4 = str6.lastIndexOf(rtrt);
console.log(index3, index4);
// repeat() 返回指定数量的数组
let syt = baby;
let syt2 = syt.repeat(3);
console.log(syt2, syt);
// replace() 数组替换 相同的替换一个
let rtr = [hahazheshiwo];
let rtr1 = rtr.replace([, *);
let rtr2 = rtr1.replace(], *);
console.log(rtr2, rtr);
// replaceAll() 数组替换 相同的全部替换
let rtr3 = [hahazheshiwo];
let rtr4 = rtr3.replaceAll(ha, “&”);
console.log(rtr4, rtr3);
// slice() 截取数组的一部分数组 [start,end)
// 前包后不包，可负数
// 第二位可省略
let wer = Thequickbrown fox jumps over the lazy dog.;
let wer1 = wer.slice(2, 6); //equi
let wer2 = wer.slice(8, -3) //brown fox jumps over the lazy d
let wer3 = wer.slice(-3, -1); //og
let wer4 = wer.slice(-3); //og.
console.log(wer4);
// substring() 截取数组的一部分数组 [start,end) 可以有负数，负数会转化成为0，再对调
let ert = helloworld;
let ert1 = ert.substring(2, 6); //llow
let ert2 = ert.substring(4); //oworld
let ert3 = ert.substring(2, -4); //he 小于0的数切换为0，再对调
console.log(ert3, ert);
// split() 数组转数组
let qwe = The quickbrown fox jumps over the lazy dog.;
let qweArr = qwe.split( );
let qwe2 = The,quickbrown,fox,jumps,;
let qweArr2 = qwe2.split(,); //[The, quickbrown, fox, jumps, ]
console.log(qweArr2);
// trim() 去除数组前后空格 trimEnd()去除后空格 trimStart()去除前空格
let rty = erouy ;
let rty1 = rty.trim();
let rty2 = rty.trimEnd();
let rty3 = rty.trimStart();
console.log(rty3, rty3.length);
// toLowerCase() 数组转小写 toUpperCase()转大写
let uio = ALphAEBT;
let uio1 = uio.toLowerCase(); //alphabet
let uio2 = erTYhi;
let uio3 = uio2.toUpperCase(); //ERTYHI
console.log(uio3);
// const zhiStr = To be, or not to be, that is the question.;
// let count = 0;
// let indexc = zhiStr.indexOf(e);
// while (indexc != -1) {
// count++;
// indexc = zhiStr.indexOf(e, indexc + 1)
// }
// console.log(`找到了${count}次`);
// Number形式
let num2 = 10.2;
//Number.isInteger 判断数字是否为整数
console.log(Number.isInteger(num2));
// Number.isNaN 判断是否为NaN
console.log(Number.isNaN(NaN));
let str7 = 348hakj;
// 数组转数字
let num3 = Number.parseInt(str7); //348
console.log(num3);
// 数组转浮点数
let str8 = 348.999uhakj;
let num4 = Number.parseFloat(str8); //348.98
console.log(num4);
// toFixed() 四舍五入指定的小数点位
let str9 = num4.toFixed(2); //348.99
console.log(str9);
// Object形式
// Object.is() 比较两个值是否相等 和 ===一致
console.log(Object.is(12, 12));
let abj = { name: zhangsan, age: 12 };
let abj2 = { name: zhangsan, age: 12 };
console.log(Object.is(abj, abj2));
// Object.assign() 合并拷贝对象 如果有相同属性的前面将前面的覆盖
// 对象中属性为基本上类型，就是深拷贝
// 对象中属性为提及类型，就是浅拷贝
let bbr = { a: 1, b: 2 };
let bbr2 = { b: 3, c: 5 };
Object.assign(bbr, bbr2);
let bbr3 = Object.assign({}, bbr2)
bbr2.b = haha;
console.log(bbr3, bbr2); //{b: 3, c: 5} {b: haha, c: 5}
let waiObj = { name: lisi, type: { age: 12, sex: 男 } };
let waiObj1 = Object.assign({}, waiObj);
waiObj1.type.sex = 女;
console.log(waiObj, waiObj1); // 两个值都是 name :”lisi”,type: {age: 12, sex: 女}
// Object.values() 取对象的属性值构成的数组 Object.keys()取对象的属性构成的数组
let trr = [er, haha, rtrt];
let trr1 = Object.values(trr);
let trr2 = { name: zhansan, type: { age: 12, sex: 男 } };
let trr3 = Object.values(trr2); //[“zhansan”,{age: 12, sex: 男}]
let trr4 = Object.keys(trr2);
console.log(trr4);
// Object.entries() 键值对数组
let trr5 = { a: somestring, b: 42 };
let trr6 = Object.entries(trr5); //[[a, somestring], [b, 42]]
console.log(trr6);
