JS regular expression application

This time I will bring you the regular expression application of JS. What are the notes for the application of JS regular expression. The following is a practical case, let’s take a look.

Today I would like to share with you some knowledge about regular expressions and their application in javascript. Regular expressions are simple but not simple. For example, when my teacher used to teach us, he said that if you get started with this thing, you can master it in 20 to 30 minutes. Once you don't get started, you won't be able to catch up in a few days. So I studied and researched it very seriously at the beginning. Unexpectedly, regular expressions not only simplify the code, but also save front-end engineers a lot of trouble in actual operations. As we all know, when users browse a page, the only thing that interacts with data is the form. Regarding form verification, there are actually many methods. Next, I will share with you two methods. One is an ordinary and cumbersome method. , one is regular expression, let’s see what effect it can bring to the form.

Let’s learn about regular expressions together.

A regular expression is an object that describes a character pattern. It is also called regular expression and conventional expression

Regular expressions use a single string to describe and match a series of strings that match a certain syntax rule. In many text editors, regular expressions are often used to retrieve and replace text that matches a certain pattern.

The characteristics of regular expressions are: 1. Very flexible, logical and functional; 2. Complex control of strings can be achieved quickly and in an extremely simple way. 3. It is relatively obscure and difficult to understand for those who are new to it.

Define regular expression 1: Normal way varreg=/expression/additional parameters reg.test(v.value)

2: Constructormethod var reg=new RegExp("expression","additional parameters) var reg=new RegExp("china");

Expression pattern 1: simple pattern var reg=/china/; 2: consistent pattern var reg=/^w $/; var reg=/^w @w .[a-zA-Z]{2,3}( .[a-zA-Z]{2,3})?$/;

Methods of the RegExp object exec searches for characters that match the regular expression, returns the found value, and determines its position. test retrieves the value specified in the string and returns true or false exec method: if no match is found, the return value is null; if a match is found, a result array is returned. /.../ represents the beginning and end of a pattern ^ matches the beginning of the string $ matches the end of the string s any whitespace character s any non-whitespace character d matches a numeric character, equivalent to [0-9] D matches any character except digits, equivalent to [^0-9] w matches a number, underscore, or alphabetic character, equivalent to [A-Za-z0-9_] W any non-word character, equivalent to [^a-zA-z0-9_] .Any character except newline character

{n} matches the previous item n times {n,} matches the previous item n times, or multiple times {n,m} matches the previous item at least n times, but not more than m times * matches the previous item 0 or more times times, equivalent to {0,}. Matches the previous item one or more times, equivalent to {1,}? Matches the previous item 0 or 1 times, which means the previous item is optional, equivalent to {0,1}

x|y matches x or y.

For example, "z|food" matches "z" or "food". "(z|f)ood" matches "zood" or "food". [xyz] Character collection. Matches any one of the characters contained. For example, "[abc]" would match the "a" in "plain". [a-z] Character range. Matches any character within the specified range. For example, "[a-z]" matches any lowercase alphabetic character in the range "a" through "z". Note: Only when a hyphen is inside a character group and appears between two characters, it can represent the range of characters; If it appears at the beginning of a character group, it can only represent the hyphen itself. (pattern) Match pattern and get this match. The obtained matches can be obtained from the generated Matches collection, using the SubMatches collection in VBScript and the $0...$9 attributes in JScript. To match parentheses characters, use "(" or ")".

I believe you have mastered the method after reading the case in this article. For more exciting information, please pay attention to other related articles on the php Chinese website!

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