table of Contents
JavaScript regular expressions
1. Create a regular expression
1.1 Method 1: Direct amount grammar
- Syntax: var reg = / pattern / attributes
- Explanation: The parameter pattern is a string that specifies a regular expression pattern or other regular expressions. Attributes is an optional parameter string containing the attribute "g", "i" and "m", are used to specify the global matching, case-insensitive match and multiple match lines.
1.2 Method 2: Create a RegExp object syntax
- Syntax: var reg = new RegExp (pattern, attributes)
- Explanation: The parameter pattern is a string that specifies a regular expression pattern or other regular expressions. Attributes is an optional parameter string containing the attribute "g", "i" and "m", are used to specify the global matching, case-insensitive match and multiple match lines.
1.3 difference:
1. The amount of direct regular expression syntax of the object is generated in the new code is compiled, it is commonly used in the usual manner to develop;
2. Using Regular generated constructor object to generate run time code.
1.4 regular expressions
1. regularization method object refers used:. RegExp object methods (String)
The method is to use a string object: String method (the RegExp object)
2. Regular properties of the object
2.1 Property
ignoreCase 返回布尔值，表示RegExp 对象是否具有标志 i
global 返回布尔值，表示RegExp对象是否具有标志g
multiline 返回布尔值，表示RegExp 对象是否具有标志 m。
lastIndex 一个整数，标识开始下一次匹配的字符位置
source 返回正则表达式的源文本（不包括反斜杠）
i 执行对大小写不敏感的匹配
g 执行全局匹配（查找所有匹配而非在找到第一个匹配后停止）。
m 执行多行匹配
正则表达式作用2.2 Application
2.2.1 verification
- When used for authentication, it is usually required before and after adding ^ and $ to match the entire string to be verified;
2.2.2 search and replace
- Search / plus whether this replacement is defined when the search request may be, in addition, it is also possible to add \ b ^ and $ instead of before and after
2.3. Match Type
2.3.1 character match
| Regular Expressions | use |
|---|---|
| […] | Find any character between the brackets |
| [^…] | Find any character not between the brackets |
| [a-z] | Find any character from lowercase a to lowercase z, |
| [A-Z] | Find any character from uppercase A to Z of capital |
| [A-z] | Find any character from uppercase A to lowercase z, |
| . | Find a single character, except for line breaks and line endings |
| \w | Find a word character, equivalent to [a-zA-Z0-9] |
| \W | Find a non-word character, equivalent to[^a-zA-Z0-9] |
| \s | Find a blank character |
| \S | Find a non-whitespace characters |
| \d | Find figures, equivalent to [0-9] |
| \D | Finding non-numeric characters, equivalent to[^0-9] |
| \b | Match a word boundary |
| \r | Find carriage return |
| \t | Find Tabs |
| \0 | Find NULL character |
| \n | Find newline |
2.3.2 repeated characters match
| Regular Expressions | use |
|---|---|
| {n,m} | Before a match at least n times, but not more than m times |
| {n,} | Match the preceding n or more times |
| {n} | N times before a match |
| n？ | Match preceding zero or 1, that is to say a front is optional, it is equivalent to {0,1} |
| n+ | Before a matching one or more times, equivalent to {1} |
| n* | Before a match zero or more times, equivalent to {0} |
| n$ | Matches any string of n ends of |
| ^n | Matches any string of the beginning of the n |
| ?=n | Immediately followed by the specified string matches any character string n |
| ?!n | Immediately thereafter not match any character string specified string n |
2.3.3 match specific digital
| Regular Expressions | use |
|---|---|
^[1-9]\d*$ |
Matching a positive integer |
^-[1-9]\d*$ |
Matching negative integer |
^-?[0-9]\d*$ |
Matching integer |
^[1-9]\d*|0$ |
0 $ matching non-negative integer (integer + 0) |
^-[1-9]\d*|0$ |
Non-matching positive integer (0 + negative integer) |
^[1-9]\d*.\d*|0.\d*[1-9]\d*$ |
Matching positive float |
^-([1-9]\d*.\d*|0.\d*[1-9]\d*)$ |
Matching negative float |
^-?([1-9]\d*.\d*|0.\d*[1-9]\d*|0?.0+|0)$ |
Match float |
^[1-9]\d*.\d*|0.\d*[1-9]\d*|0?.0+|0$ |
Matching non-negative floating point number (floating-point number n + 0) |
^(-([1-9]\d*.\d*|0.\d*[1-9]\d*))|0?.0+|0$ |
Non-matching positive float (negative float + 0) |
2.3.4 match a particular string
| Regular Expressions | use |
|---|---|
| ^ [A-Za-z] + $ | Matching string of 26 English letters |
| ^[A-Z]+$ | Matching string of uppercase letters 26 composed of |
| ^[a-z]+$ | A matching string 26 composed of lowercase letters |
| ^ [A-Za-z0-9] + $ | Matching string of numbers and English letters 26 |
| ^\w+$ | Matching string of digits, letters or underscore 26 composed of |
3 method
3.1 test method
Value specified in the search character string. Returns true or false. Value specified in the search character string. Returns true or false.
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>text</title>
</head>
<body>
<script type="text/javascript">
var reg = /123/g;
var str = 'hello123hello123';
console.log(reg.test(str));//true
console.log(reg.lastIndex);//8
console.log(reg.test(str));//true
console.log(reg.lastIndex);//16
console.log(reg.test(str));//false
console.log(reg.lastIndex);//0
</script>
</body>
</html>
//使用了g修饰符的正则表达式，表示要记录每一次搜索的位置，接着使用test方法，每次开始搜索的位置都是上一次匹配的后一个位置。3.2 exec method
A method for matching a regular expression string retrieved. It returns an array in which to store the matching results. If a match is not found, the return value is null.
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>exec</title>
</head>
<body>
<script type="text/javascript">
var str='abc';
var reg1 = /x/;
var reg2 = /a/;
console.log(reg1.exec(str));//null
console.log(reg2.exec(str));//array["a", index: 0, input: "xyz"]
</script>
</body>
</html>If the regular expression contains parentheses, the returned array will include multiple elements. First, the entire result of a successful match, followed by parentheses matching successful result, if there are multiple parentheses, the result of their match will be the success of the array elements
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>exec</title>
</head>
<body>
<script type="text/javascript">
var str='abcdabc';
var reg1 = /(a)b(c)/;
console.log(reg1.exec(str));//["abc", "a", "c", index: 0, input: "abcdabc", groups: undefined]
</script>
</body>
</html>3.3 search method
search () method for substring search character string specified, retrieving or regular expression matching substring.
Return Value: stringObject regexp with the first substring that matches the starting position.
Note: If no matches any substring, or -1.
search() 方法不执行全局匹配，它将忽略标志 g。它同时忽略 regexp 的 lastIndex 属性，并且总是从字符串的开始进行检索，这意味着它总是返回 stringObject 的第一个匹配的位置。
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>search</title>
</head>
<body>
<script type="text/javascript">
var str='abcdefgh';
console.log(str.search('h'))//7
</script>
</body>
</html>3.4match方法
match() 方法可在字符串内检索指定的值，或找到一个或多个正则表达式的匹配。该方法类似 indexOf() 和 lastIndexOf()，但是它返回指定的值，而不是字符串的位置。
字符串对象的match方法与正则对象的exec方法比较类似：但是如果正则表达式带有g修饰符，那么match方法与exec方法就有差别了:可以看到match返回了所有成功匹配的结果，但是exec方法只返回了一个。
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>match</title>
</head>
<body>
<script type="text/javascript">
var str = "abcd";
var reg1 = /a/;
var reg2 = /x/;
console.log(str.match(reg1));//a
console.log(str.match(reg2));//null
var str2 = "abcabc";
var reg3 = /a/g;
console.log(str2.match(reg3));//['a','a']
</script>
</body>
</html>3.5 replace方法
replace() 方法用于在字符串中用一些字符替换另一些字符，或替换一个与正则表达式匹配的子串。
返回值：一个新的字符串，是用 replacement 替换了 regexp 的第一次匹配或所有匹配之后得到的。
字符串 stringObject 的 replace() 方法执行的是查找并替换的操作。它将在 stringObject 中查找与 regexp 相匹配的子字符串，然后用 replacement 来替换这些子串。如果 regexp 具有全局标志 g，那么 replace() 方法将替换所有匹配的子串。否则，它只替换第一个匹配子串。
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>replace</title>
</head>
<body>
<script type="text/javascript">
var str = "aaa";
console.log(str.replace('a', 'f'));//fbcdaa
</script>
</body>
</html>3.6 split方法
split(‘字符串的分割正则','返回数组的最大成员数')；返回分割后各部分组成的数组
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>split</title>
</head>
<body>
<script type="text/javascript">
var str = "a,b,c,d,e,f";
var res = str.split(",");//以逗号来分割字符串
console.log(res);//["a", "b", "c", "d", "e", "f"]
var str2 = "a, b ,c,d";
var res2 = str2.split(/, */);//以0或对个逗号空格来分割字符串
console.log(res2);//["a", "b ", "c", "d"]
</script>
</body>
</html>3.7示例：
- 从URL中提取子域名
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>split</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>4.常用正则匹配
匹配国内电话号码：\d{3}-\d{8}|\d{4}-\d{7}
如 0511-4405222 或 021-87888822
匹配QQ号：[1-9][0-9]{4,}
从10000开始
邮政编码：[1-9]\d{5}(?!\d)
邮政编码为6位数字
匹配身份证：/^(\d{14}|\d{17})(\d|[xX])$/
匹配规则：身份证号码有15位或者18位，其中最后一位可能是X，其他全是数字
匹配ip地址：\d+.\d+.\d+.\d+
匹配帐号是否合法(字母开头，允许5-16字节，允许字母数字下划线)：^[a-zA-Z][a-zA-Z0-9_]{4,15}$ 表单验证时很实用
匹配中文字符： /[\u4E00-\u9FA5\uf900-\ufa2d]/
使用 Unicode，必须使用\u开头，接着是字符编码的四位16进制表现形式
匹配Email地址：
/^([a-zA-Z_0-9-])+@([a-zA-Z_0-9-])+(.[a-zA-Z_0-9-])+$/
邮箱的规则是: 由3部分组成
由1个或者多个字母数字下划线和杠 + @ + 1个或者多个字母数字下划线和杠 + . + 1个或者多个字母数字下划线和杠
匹配网址URL：[a-zA-z]+://[^\s]*
判断字符串是不是由数字组成: /^\d*$/
限制文本框只能输入数字和小数点(二位小数点):
/^\d*.?\d{0,2}$/
说明：开头有0个或者多个数字，(?表示匹配前一项0次或者多次)中间有0个或者1个小数点，小数点后面有0个或者最多2个数字
用户名正则: /^[\u4E00-\u9FA5\uf900-\ufa2d\w]{4,16}$/
匹配规则：只能是中文，英文，数字，下划线，4-16个字符
匹配中文字符正则：/[\u4E00-\u9FA5\uf900-\ufa2d]/
\w是 匹配英文，数字，下划线
匹配英文地址:/^[a-zA-Z][.a-zA-Z\s,0-9]*?[a-zA-Z]+/匹配规则：包含点，字母，空格，逗号，数字，但是开头和结尾必须为字母分析：开头必须为字母可以这样写/[a−zA−Z]/结尾必须为字母可以这样写：/[a−zA−Z]+/
中间包含点，字母，空格，逗号，数字的正则：/[.a-zA-Z\s,0-9]*?/
外面的*号是0个或者多个，后面的问号? 代表可有可无;有就匹配，没有就不匹配;
匹配价格:/^\d*(.\d{0,2})?$/
匹配规则: 开头有0个或者多个数字，中间可能有一个小数点，后面有可能有0-2位小数
单词的首字母大写:/\b(\w)|\s(\w)/g
验证日期格式:/^\d{4}[-\/]\d{1,2}[-\/]\d{1,2}$/
日期格式有2种 第一种是yyyy-mm-dd 或 yyyy/mm/dd
分析:月和天数可以有1位或者2位