js中的正則表達(dá)式入門(mén)(大量實(shí)例代碼)

//找出這個(gè)字符串中的所有數(shù)字
var str = 'abc123de45fgh6789qqq111';
//方法1
 function findNum(str) {
 var tmp = '',
  arr = [];
 for (var i = 0; i  str.length; i++) {
  var cur = str[i];
  if (!isNaN(cur)) {
  tmp += cur;
  } else {
  if (tmp) {
   arr.push(tmp);
   tmp = '';
  }
  }
 }
 if (tmp) {
  arr.push(tmp)
 }
 return arr;
 }
 console.log(findNum(str))
 //["123", "45", "6789", "111"]
 
//方法2 使用正則表達(dá)式
 var reg = /\d+/g;
 console.log(str.match(reg))
 // ["123", "45", "6789", "111"]

var reg = /pattern/flags
 // 字面量創(chuàng)建方式
 var reg = new RegExp(pattern,flags);
 //實(shí)例創(chuàng)建方式
 
 pattern:正則表達(dá)式 
 flags:標(biāo)識(shí)(修飾符)
 標(biāo)識(shí)主要包括：
 1. i 忽略大小寫(xiě)匹配
 2. m 多行匹配，即在到達(dá)一行文本末尾時(shí)還會(huì)繼續(xù)尋常下一行中是否與正則匹配的項(xiàng)
 3. g 全局匹配 模式應(yīng)用于所有字符串，而非在找到第一個(gè)匹配項(xiàng)時(shí)停止

var regParam = 'cm';
var reg1 = new RegExp(regParam+'1');
var reg2 = /regParam/;
console.log(reg1); // /cm1/
console.log(reg2); // /regParam/

var reg1 = new RegExp('\d'); // /d/ 
var reg2 = new RegExp('\\d') // /\d/
var reg3 = /\d/;  // /\d/

var str = '1223334444';
var reg = /\d{2}/g;
var res = str.match(reg);
console.log(res) //["12", "23", "33", "44", "44"]

var str =' 我是空格君 ';
var reg = /^\s+|\s+$/g; //匹配開(kāi)頭結(jié)尾空格
var res = str.replace(reg,'');
console.log('('+res+')') //(我是空格君)

var str1 = 'abc';
var str2 = 'dbc';
var str3 = '.bc';
var reg = /[ab.]bc/; //此時(shí)的.就表示.
reg.test(str1) //true
reg.test(str2) //false
reg.test(str3) //true

[12]表示1或者2 不過(guò)[0-9]這樣的表示0到9 [a-z]表示a到z
例如:匹配從18到65年齡段所有的人
var reg = /[18-65]/; // 這樣寫(xiě)對(duì)么
reg.test('50')
reg = /(18|19)|([2-5]\d)|(6[0-5])/;

var str = 'abbbbAAbcBCCccdaACBDDabcccddddaab';
 str = str.toLowerCase().split('').sort(function(a,b){return a.localeCompare(b)}).join('');

 var reg = /(\w)\1+/ig;
 var maxStr = '';
 var maxLen = 0;
 str.replace(reg,function($0,$1){
 var regLen = $0.length;
 if(regLen>maxLen){
  maxLen = regLen;
  maxStr = $1;
 }else if(maxLen == regLen){
  maxStr += $1;
 }
 })
 console.log(`出現(xiàn)最多的字母是${maxStr},共出現(xiàn)了${maxLen}次`)

var str = 'aaabbb';
var reg = /(a+)(?:b+)/;
var res =reg.exec(str);
console.log(res)
//["aaabbb", "aaa", index: 0, input: "aaabbb"]
//只捕獲第一個(gè)小分組的內(nèi)容

var str = '123aaa456';
var reg = /\d+/; //只捕獲一次,一次盡可能多的捕獲
var res = str.match(reg)
console.log(res)
// ["123", index: 0, input: "123aaa456"]
reg = /\d+?/g; //解決貪婪性、懶惰性
res = str.match(reg)
console.log(res)
// ["1", "2", "3", "4", "5", "6"]

var str = 'abc';
var reg = /\w+/;
console.log(reg.test(str)); //true

var str = 'abc123cba456aaa789';
var reg = /\d+/;
console.log(reg.exec(str))
// ["123", index: 3, input: "abc123cba456aaa789"];
console.log(reg.lastIndex)
// lastIndex : 0 

reg.exec捕獲的數(shù)組中 
// [0:"123",index:3,input:"abc123cba456aaa789"]
0:"123" 表示我們捕獲到的字符串
index:3 表示捕獲開(kāi)始位置的索引
input 表示原有的字符串

var str = 'abc123cba456aaa789';
var reg = /\d+/g; //此時(shí)加了標(biāo)識(shí)符g
console.log(reg.lastIndex)
// lastIndex : 0 

console.log(reg.exec(str))
// ["123", index: 3, input: "abc123cba456aaa789"]
console.log(reg.lastIndex)
// lastIndex : 6

console.log(reg.exec(str))
// ["456", index: 9, input: "abc123cba456aaa789"]
console.log(reg.lastIndex)
// lastIndex : 12

console.log(reg.exec(str))
// ["789", index: 15, input: "abc123cba456aaa789"]
console.log(reg.lastIndex)
// lastIndex : 18

console.log(reg.exec(str))
// null
console.log(reg.lastIndex)
// lastIndex : 0

var str = '2017-01-05';
var reg = /-(\d+)/g
// ["-01", "01", index: 4, input: "2017-01-05"]
"-01" : 正則捕獲到的內(nèi)容
"01" : 捕獲到的字符串中的小分組中的內(nèi)容

//match和exec的用法差不多
var str = 'abc123cba456aaa789';
var reg = /\d+/;
console.log(reg.exec(str));
//["123", index: 3, input: "abc123cba456aaa789"]
console.log(str.match(reg));
//["123", index: 3, input: "abc123cba456aaa789"]

var str = 'abc123cba456aaa789';
var reg = /\d+/g;
console.log(reg.exec(str));
// ["123", index: 3, input: "abc123cba456aaa789"]
console.log(str.match(reg));
// ["123", "456", "789"]

String.prototype.myMatch = function (reg) {
 var arr = [];
 var res = reg.exec(this);
 if (reg.global) {
 while (res) {
  arr.push(res[0]);
  res = reg.exec(this)
 }
 }else{
 arr.push(res[0]);
 }
 return arr;
}

var str = 'abc123cba456aaa789';
var reg = /\d+/;
console.log(str.myMatch(reg))
// ["123"]

var str = 'abc123cba456aaa789';
var reg = /\d+/g;
console.log(str.myMatch(reg))
// ["123", "456", "789"]

var str = 'abc';
var reg = /(a)(b)(c)/;

console.log( str.match(reg) );
// ["abc", "a", "b", "c", index: 0, input: "abc"]
console.log( reg.exec(str) );
// ["abc", "a", "b", "c", index: 0, input: "abc"]


當(dāng)有全局g的情況下
var str = 'abc';
var reg = /(a)(b)(c)/g;
console.log( str.match(reg) );
// ["abc"]
console.log( reg.exec(str) );
// ["abc", "a", "b", "c", index: 0, input: "abc"]

var str = 'a111bc222de';
var res = str.replace(/\d/g,'Q')
console.log(res)
// "aQQQbcQQQde"

//replace的第二個(gè)參數(shù)也可以是一個(gè)函數(shù)
str.replace(reg,fn);

var str = '2017-01-06';
str = str.replace(/-\d+/g,function(){
 console.log(arguments)
})

//控制臺(tái)打印結(jié)果：
["-01", 4, "2017-01-06"]
["-06", 7, "2017-01-06"]
"2017undefinedundefined"
//從打印結(jié)果我們發(fā)現(xiàn)每一次輸出的值似乎跟exec捕獲時(shí)很相似，既然與exec似乎很相似，那么似乎也可以打印出小分組中的內(nèi)容嘍 

var str = '2017-01-06';
str = str.replace(/-(\d+)/g,function(){
 console.log(arguments)
})
["-01", "01", 4, "2017-01-06"]
["-06", "06", 7, "2017-01-06"]
"2017undefinedundefined"
//從結(jié)果看來(lái)我們的猜測(cè)沒(méi)問(wèn)題。

(function(pro){
 function queryString(){
 var obj = {},
  reg = /([^?#+]+)=([^?#+]+)/g;
 this.replace(reg,function($0,$1,$2){
  obj[$1] = $2;
 })
 return obj;
 }
 pro.queryString = queryString;
}(String.prototype));

// 例如 url為 https://www.baidu.com?a=1b=2
// window.location.href.queryString();
// {a:1,b:2}

var str = "i'm singing and dancing";
var reg = /\b(\w+(?=ing\b))/g
var res = str.match(reg);
console.log(res)
// ["sing", "danc"]

var str = 'abc';
var reg = /a(?=b)c/;
console.log(res.test(str)); // false

// 這個(gè)看起來(lái)似乎是正確的，實(shí)際上結(jié)果是false

var str = 'nodejs';
var reg = /node(?!js)/;
console.log(reg.test(str)) // false

var str = '￥998$888';
var reg = /(?=\$)\d+/;
console.log(reg.exec(str)) //888

var str = '￥998$888';
var reg = /(?!\$)\d+/;
console.log(reg.exec(str)) //998