正则表达式

声明一个正则表达式

字面量声明

const rex = /pattern/;

构造函数声明

const rex = new RegExp(pattern);

匹配模式

字符集合

let rex = /[bc]t/g;

let string = "actionbatbtctat";

console.log(string.match(rex)); // [ 'ct', 'bt', 'ct' ]

拓展

[a-z] 从小写a-z
[A-Z] 大写A-Z
[0-9] 0-9
[^a] 除了a以外的

符号范围：[#$%&@]；
混合范围：[a-zA-Z0-9]，匹配所有数字、大小写字母中的任意字符。

量词

let rex = /[a-z]{2}/g;

let string = "actionbbatbcctctat";

console.log(string.match(rex)); // [ 'ac', 'ti', 'on', 'bb', 'at', 'bc', 'ct', 'ct', 'at' ]

拓展

{3} 出现次数为最多3次
{1,4} 1 <= 出现次数 <= 4
{1,} 最少出现1次，简写 +
{0,} 至少0次，简写*
{0,1} 最少0次，最多1次，简写?

元字符

特殊字符

位置匹配

修饰符

实例方法

test() 和 exec()

const regex1 = /a/gi;
const regex2 = /hello/gi;
const str = "Action speak louder than words";

console.log(regex1.test(str)); // true
console.log(regex2.test(str)); // false

const regex1 = /a/gi;
const regex2 = /hello/gi;
const str = "Action speak louder than words";

console.log(regex1.exec(str)); // ['A', index: 0, input: 'Action speak louder than words', groups: undefined]
console.log(regex2.exec(str)); // null

字符串方法

search()

const regex1 = /a/gi;
const regex2 = /p/gi;
const regex3 = /m/gi;
const str = "Action speak louder than words";

console.log(str.search(regex1)); // 输出结果：0
console.log(str.search(regex2)); // 输出结果：8
console.log(str.search(regex3)); // 输出结果：-1

match()

const regex1 = /a/gi;
const regex2 = /a/i;
const regex3 = /m/gi;
const str = "Action speak louder than words";

console.log(str.match(regex1)); // 输出结果：['A', 'a', 'a']
console.log(str.match(regex2)); // 输出结果：['A', index: 0, input: 'Action speak louder than words', groups: undefined]
console.log(str.match(regex3)); // 输出结果：null

replace()

const regex = /a/g;
const str = "Action speak louder than words";

console.log(str.replace(regex, "A")); // 输出结果：Action speAk louder thAn words