js正则分组

傷城~ 2023-06-18 04:59 2阅读 0赞

本文转载于[https://www.cnblogs.com/Vibge/p/9831953.html][https_www.cnblogs.com_Vibge_p_9831953.html]

js 正则表达式分组  
正则表达式分组：通俗的就是正则表达式中（）包起来的内容表示一个分组

例如：

var reg = /^(\d{2})$/;
    var asd = reg.test('12');
    console.log(asd); //true

1、利用正则表达式优雅的表达重复的字符串

var reg2 = /^(SD)\d{4}(-\d{4}){3}$/;
    console.log(reg2.test('SD0214-0000-0000-0000')); //true

例如：`/^(ha){3}$/` 等同于 `/^hahaha$/`

2 、多个候选表达式

var reg3 = /^I come from (hunan|hubei|zhejiang)$/;
    console.log(reg3.test('I come from hunan'));

3、分组的分类：捕获型`()`;非捕获型`(?:)`;正向前瞻性`(?=)`;反向前瞻性`(?!)`

// 1、获取
    var reg4 = /^(\d{4})-(\d{2})-(\d{2})$/
    var data = '2018-10-17';
    reg4.test(data);
    console.log(RegExp.$1); // 输出 2018
    console.log(RegExp.$2); // 输出 10
    console.log(RegExp.$3); // 输出 17
    
    // 2、结合replace方法做字符串自定义转换
    var date2 = '2018/04/18';
    var reg5  =/^(\d{4})\/(\d{2})\/(\d{2})$/;
    var dateStr = date2.replace(reg5, '$1-$2-$3') //"2018-04-18";
    console.log(dateStr); 
    
    // 3、反向引用
    var reg6 = /^(\w{3}) is \1$/;
    console.log(reg6.test('kid is kid')); // true
    console.log(reg6.test('kid is dik')); // false
    
    // 如果越界或者编号不存在，则被解析为普通的表达式
    var reg7 = /^(\w{3}) is \6$/;
    console.log(reg7.test('kid is \6')); // true
    console.log(reg7.test('kid is kid')); // false
    
    // 4、非捕获型分组
    var reg8 = /^(?:\d{4})-(\d{2})-(\d{2})$/;
    var date3 = '2018-10-18';
    reg8.test(date3);  //true
    console.log(RegExp.$1); //10
    console.log(RegExp.$2); //18
     
    // 5、正向与反向前瞻性分组; 正向，站在原地往前看，如果前方是指定的东西就返回true，否则返回false
    var reg9 = /^kid is a (?=boy)/;
    console.log(reg9.test('kid is a boy')); // true
    console.log(reg9.test('kid is a girl'));// false
    
    //6、正向与反向前瞻性分组例子
    let reg = /(?=o)/g
    let str = 'hello world'
    let s = str.replace(reg,'A')
    console.log(s)    //输出hellAo wAorld
    
    let reg = /l(?=o)/g
    let str = 'hello world'
    let s = str.replace(reg,'A')
    console.log(s)     //输出helAo world
    
    //反向前瞻型分组：你站在原地往前看，如果前方不是指定的东西则返回true，如果是则返回false
    let reg = /(?!l)/g
    let str = 'hello'
    let s = str.replace(reg,'A')
    console.log(s)    //输出AhAellAoA
    
    let reg = /l(?!o)/g
    let str = 'hello'
    let s = str.replace(reg,'A')
    console.log(s)    //输出heAlo

[https_www.cnblogs.com_Vibge_p_9831953.html]: https://www.cnblogs.com/Vibge/p/9831953.html