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Today, I will talk to you about how to use javascript to get specified characters, many people may not know much about it. In order to make you understand better, the editor has summarized the following content for you. I hope you can get something according to this article.

Javascript method to get the specified characters: 1, through the substring method to extract the string between the two specified subscript characters; 2, through the substr method to take the specified number of characters; 3, through the slice method to extract a part of the string.

This article operating environment: windows7 system, javascript1.8.5 version, Dell G3 computer.

How does javascript get the specified character?

Javascript extracts strings, and JavaScript intercepts strings in detail.

1. Substring ()

(1) used to extract characters that are mediated between two specified subscripts. Syntax: stringObject.substring (start,stop)

Start: required. A non-negative integer that specifies the position of the substring to be extracted in the first character in the stringObject.

Stop; is optional. A non-negative integer that is 1 more positioned in stringObject than the last character of the substring to be extracted. If this parameter is omitted

Then the returned substring goes all the way to the end of the string.

(2) return value

A new string containing a substring of stringObject whose content is the length of all characters from start to stop-1

Subtract start for stop. (subscript starts at 0)

The substring returned by the substring () method includes the character at start, but not the character at end. If the parameter start is equal to end, the method returns

What is returned is an empty string (that is, a string of length 0). If start is larger than end, the method swaps these two parameters before extracting the substring.

Important: unlike the slice () and substr () methods, substring () does not accept negative parameters.

Example 1:

Var str= "Hello world!" [xss_clean] (str.substring (3)) / / output lo world!

Example 2:

Var str= "Hello world!" [xss_clean] (str.substring (3p7)) / / output lo w

Recommended study: "javascript basic course"

2. Substr () method

(1) the substr () method extracts a specified number of characters from a string starting with the start subscript. StringObject.substr (start,length)

Start: required. The starting subscript of the substring to be extracted. Must be a numeric value. If it is a negative number, the parameter declares that it starts at the end of the string

Location. That is,-1 refers to the last character in the string,-2 refers to the penultimate character, and so on.

Length: optional. The number of characters in the substring. Must be a numeric value. If this parameter is omitted, the string from the beginning to the end of the stringObject is returned.

(2) return value

A new string containing lenght characters starting at the start of stringObject (including the characters referred to by start). If it doesn't refer to

Set lenght, then the returned string contains the characters from start to the end of stringObject.

(3) the parameter substr () specifies the start position and length of the substring, so it can be used instead of substring () and slice ().

(4) example 1:

Var str= "Hello world!" [xss_clean] (str.substr (3)) / / output lo world!

Example 2:

Var str= "Hello world!" [xss_clean] (str.substr (3p7)) / / output lo worl

3. Slice () method

(1) you can extract a part of a string and return the extracted part with a new string. StringObject.slice (start,end)

Start: the starting subscript of the fragment to be extracted. If it is a negative number, this parameter specifies the position from the end of the string. That is to say,

-1 refers to the last character of the string,-2 refers to the penultimate character, and so on.

End: the subscript immediately following the end of the clip to be extracted. If this parameter is not specified, the substring to be extracted includes the characters from start to the end of the original string

String. If the parameter is negative, it specifies the position from the end of the string.

(2)

Return value

A new string. Includes all characters of the string stringObject from the beginning of start (including start) to the end of end (excluding end).

(3) example 1:

Var str= "Hello happy world!" [xss_clean] (str.slice (6)) / / output: happy world!

Example 2:

Var str= "Hello happy world!" [xss_clean] (str.slice (6 Magi 11)) / / output: happy

Description

The methods slice (), substring (), and substr () (not recommended) of the String object can all return the specified portion of the string. Slice () is better than substring ()

Be flexible because it allows you to use negative numbers as parameters. Slice () is different from substr () in that it specifies the substring with the position of two characters, while

Substr () specifies the substring with character position and length.

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