4.07字符串与数组的一些常用方法

concat()拼装
let str = "html".concat("css","js","php","!",888);
htmlcssjsphp!888

slice(start,end)取子串

str = "hello php.cn";
let res = str.slice(0,5);
console.log(res);//hello
res = str.slice(6);
console.log(res);//php.cn

3.substr(start,size)取子串

res = str.substr(0,5);
console.log(res);//hello

4.trim():删除字符串两边的空白字符

let pw = "    888    ";
console.log(pw.length);//11
console.log(pw.trim());//888

5.split() 将字符串打散成数组

res = str.split("");
console.log(res);//["h", "e", "l", "l", "o", " ", "p", "h", "p", ".", "c", "n"]
let email = "demo@mail.com";
res = email.split("@");
console.log(res);//["demo", "mail.com"]
console.log('userName = ',res[0]);//userName =  demo
console.log('emailAddress = ',res[1]);//emailAddress =  mail.com

6.replace() 替换字符串内容

res = email.replace("demo","admin")
console.log(res);// admin@mail.com

数组方法

1.pop() 从数组中删除最后一个元素

arr = ["Banana", "Orange", "Apple", "Mango"];
arr.pop();
console.log(arr);// ["Banana", "Orange", "Apple"]

2.push() 在结尾处向数组添加一个新的元素

arr.push("Cherry");
console.log(arr);// ["Banana", "Orange", "Apple", "Cherry"]

3.shift() 删除首个数组元素

arr.shift();
console.log(arr);// ["Orange", "Apple", "Cherry"]

4.unshift() 将新元素添加到数组的开头

arr.unshift("Lemon");
console.log(arr);// ["Lemon", "Orange", "Apple", "Cherry"]

数组方法

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