Js regular expression knowledge summary_javascript skills

Regular expression:

1. What is RegExp? RegExp is the abbreviation of regular expression. RegExp objects are used to specify the content to be retrieved from text.

2. Define RegExp: var variable name=new RegExp();

3. The RegExp object has 3 methods:

1) test() retrieves the specified value in the string, and the return value is true or false.

Copy code The code is as follows:

var p1=new Reg("e");
document.write(Reg.test("welcome to China!"));

2) exec()

Copy code The code is as follows:

var p1=new Reg("e");
document.write(Reg.exec("welcome to China!"));

3) compile()

Copy code The code is as follows:

var p1=new Reg("e");
document.write(Reg.compile("welcome to China!"));

4. Modifier

1) i performs case-insensitive matching

2) g performs global matching

3) m performs multi-line matching

5. Square brackets (used to find characters within a certain range)

1) [abc] Find any characters between square brackets

2) [^abc] finds any characters not between square brackets

3) [0-9] Find any number between 0-9

4) [a-z] Find any lowercase character between a-z

5) [A-Z] Find any uppercase character between A-Z

6) [A-z] Find any character between uppercase A-lowercase z

7) [adgk] Find any character within the given set

8) [^adgk] Find any character outside the given set

9) (red|biue|green) Find any given option

6. Metacharacters

1) w: Find word characters

2) W: Find non-word characters

3) d: Find numbers

4) D: Find non-numeric characters

7. Quantifier

n matches any string containing at least one n.

n* matches any string containing zero or more n.

n? matches any string containing zero or one n.

n{X} matches a string containing X sequences of n.

n{X,Y} matches a string containing X or Y sequences of n.

n{X,} matches a string containing at least X sequences of n.

n$ matches any string ending in n.

^n matches any string starting with n.

?=n matches any string immediately followed by the specified string n.

?!n matches any string that is not immediately followed by the specified string n.

[Exercise 1] Determine whether the format of the entered ID card is correct

Copy code The code is as follows:

Please enter your ID number:





<script><br> function test()<br> {<br> var reg=new RegExp(/^[0-9]{17}[0-9|X]$/);<!--Format of regular expression: starting with /^, ending with $/, numbers, Use square brackets for letter ranges --><br> var text=document.getElementById("shenfen").value;<!--The id of the string entered in the text box corresponds to the id of the text box--><br> //Determine whether the region is legal (use if...else) <br> if(reg.test(text))<br> {<br> alert("Input correct")<br> }<br> else<br> {<br> alert("Input error");<br> }<br> }<br> </script>

Rendering:

[Exercise 2] Determine whether the entered email format is correct

Copy code The code is as follows:

Please enter your email address:




<script><br> function y()<br> {<br> var yx=new RegExp(/^[0-9|A-z|_]{1,17}@[A-z|0-9]{1,5}.(com|cn|net|org|cc)$/) ;<br> var shuru=document.getElementById("youxiang").value; <!--Define variables and call the entire function, and the variables must be written in the function--><br> if(yx.test(shuru))<!--test regular expression method--><br> {<br> alert("zhengque");<br> }<br> else<br> {<br> alert("cuowu");<br> }<br> }<br> </script>

Rendering:

Relatively speaking, regular expressions in js are a very important point. Many places need to cooperate with regular expressions, so friends must learn this content well.