【JavaScript】08-js字符串处理

08-js字符串处理

1.字符串转换

let num = 28;

let str1 = num.toString();

let str2 = String(num);

let str3 = "" + num;

2.字符串分隔

let str4 = "hello,html,java,html,js";

let array1 = str4.split(",");//根据，号分隔

let array2 = str4.split();//将字符串变成数组

let array3 = str4.split("",6);//按照每个字符切割，切割到6位

3.字符串替换

let replaceStr = str4.replace("java", "css");

4.获取字符串长度

let length = str4.length;

5.查询子字符串

let index1 = str4.indexOf("l", 4);//查询第一个符合查询条件的，从第4位开始查找。

let index2 = str4.lastIndexOf("l");查找最后一个符合条件的元素。

6.获取指定位置的字符

let char1 = str4.charAt(5);

7.字符串匹配(使用正则表达式匹配)

let  result1 = str4.match("java");
console.log(result1);
console.log(result1.index);

let result2 = str4.search("java");
console.log(result2);

8.字符串切割

let str = str4.substring(5);//从索引为5开始截取

let str = str4.substring(5, 9);//包前不包后

let str = str4.substr(5);//从索引为5开始截取

let str = str4.substr(5, 9);//从索引5的位置开始截取9个字符

let str = str4.slice(5);//从索引为5开始截取

let str = str4.slice(-5);//从后往前计算，最后一位是-1

let str = str4.slice(5, 9);

let str = str4.slice(-5, -1);

9.字符串拼接

let str = str4 + ",python";

let str = str4.concat(",python");

10.字符串去空格

let str5 = "    hello world    ";
let str = str5.trim();

11.字符串转大小写

"abc".toUpperCase();//转大写
"DEF".toLowerCase();//转小写

es6新增函数

1.判断字符串是否包含指定子串

let str6 = "hello world hi js";
let result = str6.includes("hi");//true

2.判断字符串开始和结束是否是指定子串

str6.startsWith("hello");//true
str6.endsWith("js");//true

3.字符串重复

let str = "js,".repeat(6);//使字符串重复6次

4.补全字符串

let str7 = "hello";
let str = str7.padStart(10, "A");//会在前面补5个A

let str = str7.padEnd(10, " ");//会在后面补5个空格

5.字符串模板

let str8 = `${str7} js`;//`和数据库里面的标识符一样
let x = 10;
let y = 18;
let result = `x + y = ${x + y}`;