js正則表達式學(xué)習(xí)和總結(jié)(必看篇)

!DOCTYPE html>
html>
head>
 meta charset="utf-8">
 meta http-equiv="X-UA-Compatible" content="IE=edge">
 title>test方法/title>
/head>
body>
 script type="text/javascript">
  var reg = /abc/g;
  var str = "123abc456abc";
  console.log(reg.lastIndex);//0
  console.log(reg.test(str));//true
  console.log(reg.lastIndex);//6
  console.log(reg.test(str));//true
  console.log(reg.lastIndex);//12
  console.log(reg.test(str));//false
 /script>
/body>
/html>

!DOCTYPE html>
html>
head>
 meta charset="utf-8">
 meta http-equiv="X-UA-Compatible" content="IE=edge">
 title>test方法/title>
/head>
body>
 script type="text/javascript">
  console.log(new RegExp('').test('abc'));//true
  console.log(/''/.test('abc'));//false
  console.log(/''/.test("''"));//true
 /script>
/body>
/html>

!DOCTYPE html>
html>
head>
 meta charset="utf-8">
 meta http-equiv="X-UA-Compatible" content="IE=edge">
 title>exec方法/title>
/head>
body>
 script type="text/javascript">
 var str = "xyz";
 var reg1 = /x/;
 var reg2 = /a/;
 var res1 = reg1.exec(str);
 var res2 = reg2.exec(str);
 console.log(res1);//["x", index: 0, input: "xyz"]
 console.log(res2);//null
 /script>
/body>
/html>

!DOCTYPE html>
html>
head>
 meta charset="utf-8">
 meta http-equiv="X-UA-Compatible" content="IE=edge">
 title>exec方法2/title>
/head>
body>
 script type="text/javascript">
 var str = 'abcdabc';
 var reg = /(a)b(c)/;
 var res = reg.exec(str);
 console.log(res);//["abc", "a", "c", index: 0, input: "abcdabc"]
 /script>
/body>
/html>

!DOCTYPE html>
html>
head>
 meta charset="utf-8">
 meta http-equiv="X-UA-Compatible" content="IE=edge">
 title>search方法/title>
/head>
body>
 script type="text/javascript">
 var str = "abcdcef";
 console.log(str.search(/c/g));//2
  /script>
/body>
/html>

!DOCTYPE html>
html>
head>
 meta charset="utf-8">
 meta http-equiv="X-UA-Compatible" content="IE=edge">
 title>match方法/title>
/head>
body>
 script type="text/javascript">
 var str = "abcd";
 var reg1 = /a/;
 var reg2 = /x/;
 console.log(str.match(reg1));//["a", index: 0, input: "abcd"]
 console.log(str.match(reg2));//null

 var str = "abcdabc";
 var reg = /a/g;
 console.log(str.match(reg));//["a", "a"]
 console.log(reg.exec(str));//["a", index: 0, input: "abcdabc"]
  /script>
/body>
/html>

!DOCTYPE html>
html>
head>
 meta charset="utf-8">
 meta http-equiv="X-UA-Compatible" content="IE=edge">
 title>replace方法/title>
/head>
body>
 script type="text/javascript">
 var str = "xxx";
 console.log(str.replace('x','y'));//yxx
 console.log(str.replace(/x/,'y'));//yxx
 console.log(str.replace(/x/g,'y'));//yyy
  /script>
/body>
/html>

!DOCTYPE html>
html>
head>
 meta charset="utf-8">
 meta http-equiv="X-UA-Compatible" content="IE=edge">
 title>replace中的特殊字符替換/title>
/head>
body>
 script type="text/javascript">
 //用子表達式替換：$1和$2
 //正則表達式中()就是一個子表達式，$1對應(yīng)是第一個表達式的內(nèi)容，即java，$2為script
 var str = "javascript";
 console.log(str.replace(/(java)(script)/,'$2$1')); //輸出：scriptjava 
 //$ 為正則表達式匹配的字符串
 //正則表達式通過直接量java來匹配，匹配結(jié)果為java，則 $的值為java，然后用字符串$-來替換匹配的字符串
 var str1 = "javascript";
 console.log(str1.replace(/java/,'$-')); //輸出：java-script

 var str2 = "javascript";
 // $`為匹配子串a(chǎn)va的左側(cè)文本，則為j
 console.log(str2.replace(/ava/,"$`")); //輸出：jjscript
 // $'為匹配子串a(chǎn)va的右側(cè)文本，則為script
 console.log(str2.replace(/ava/,"$'")); //輸出：jscriptscript
 // $$為直接量符號，即插入一個$符號
	console.log(str2.replace(/ava/,"$$"));//輸出：j$script
 /script>
/body>
/html>

!DOCTYPE html>
html>
head>
 meta charset="utf-8">
 meta http-equiv="X-UA-Compatible" content="IE=edge">
 title>replace的參數(shù)replacement是函數(shù)/title>
/head>
body>
 script type="text/javascript">
function replacer(match, a1, a2, a3, index, string) {
 return [a1, a2, a3].join(' ~ ');
}
 var str = 'xyz45678%$^';
 var reg = /([^\d]*)(\d*)([^\w]*)/
var res = str.replace(reg, replacer); 
console.log(res);//xyz ~ 45678 ~ %$^
 /script>
/body>
/html>

!DOCTYPE html>
html>
head>
 meta charset="utf-8">
 meta http-equiv="X-UA-Compatible" content="IE=edge">
 title>split方法/title>
/head>
body>
 script type="text/javascript">
 var str = 'a,b , c,d';
 var res = str.split(",");//以逗號來分割字符串
 console.log(res);//["a", "b ", " c", "d"]

 var str1 = 'a,b , c,,d';
 var res1 = str1.split(/,*/);//以0或多個逗號來分割字符串
 console.log(res1);//["a", "b", " ", " ", "c", "d"]

 var str2 = 'a, b,c, d';
 var res2 = str2.split(/, */);//以0或?qū)€逗號空格來分割字符串
 console.log(res2);//["a", "b", "c", "d"]

 var str3 = 'a, b,c, d';
 var res3 = str3.split(/, */,2);//以0或?qū)€逗號空格來分割字符串，同時限制返回數(shù)組中最多有兩項
 console.log(res3);//["a", "b"]
  /script>
/body>
/html>

!DOCTYPE html>
html>
head>
 meta charset="utf-8">
 meta http-equiv="X-UA-Compatible" content="IE=edge">
 title>split方法2/title>
/head>
body>
 script type="text/javascript">
 var str = "x@@xx@xx@@";
 var res = str.split(/x*/);//以0或者對個x為分隔符
 console.log(res);//["", "@", "@", "@", "@", "@"]

 var res1 = str.split(/(x*)/);//如果加上括號則括號匹配的部分也就是分割規(guī)則也會作為數(shù)組成員返回
 console.log(res1);//["", "x", "@", "", "@", "xx", "@", "xx", "@", "", "@"]
  /script>
/body>
/html>

!DOCTYPE html>
html>
head>
 meta charset="utf-8">
 meta http-equiv="X-UA-Compatible" content="IE=edge">
 title>字符串中出現(xiàn)次數(shù)最多的字符/title>
/head>
body>
script type="text/javascript">
var str = 'mmmmmmmmaaammmmmmmmmbbbbsccc';
function most(str) {
 var arr = str.split('');
 str = arr.sort().join('');//將字符串按單個字符分割，然后排序組合，經(jīng)過這一步，相同的字符就會排列到一起
 var reg = /(\w)\1+/g;
 var num = 0;
 var value = '';
 str.replace(reg, function (a,b) {
 // console.log(a);
  if (numa.length) {
   num = a.length;
   value = b;
  }
 });
 return '出現(xiàn)次數(shù)最多的字符是' + value + '出現(xiàn)了' + num + '次';
}
console.log(most(str));
 /script>
/body>
/html>

!DOCTYPE html>
html>
head>
 meta charset="utf-8">
 meta http-equiv="X-UA-Compatible" content="IE=edge">
 title>從url中提取子域名/title>
/head>
body>
 script type="text/javascript">
  var url = "http://www.abc.com";
  var reg = /[^.]+/;//匹配除了.之外的其他字符
  var res = reg.exec(url)[0].substr(7);
  console.log(reg.exec(url));//["http://www", index: 0, input: "http://www.abc.com"]
  console.log(res);//www
 /script>
/body>
/html>

!DOCTYPE html>
html>
head>
 meta charset="utf-8">
 meta http-equiv="X-UA-Compatible" content="IE=edge">
 title>給字符串加千分符/title>
/head>
body>
 script type="text/javascript">
 var str = "12345678912312";
 function fn(str){
    var reg = /(?=(?!b)(\d{3})+$)/g;
    return str.replace(reg,',');
   }
   var res = fn(str);
   console.log(res);//12,345,678,912,312
 /script>
/body>
/html>