Briefly introduce the methods of substring and substr in js

This article mainly introduces the substring and substr methods in js, and describes and explains the substring and substr methods. Interested friends can refer to Let’s take a look

1. substring method: is used to extract the characters between two specified subscripts in the string substring(start,end)

Start and end positions, zero-based Index

Parameter Description
start Required. A non-negative integer that specifies the position in stringObject of the first character of the substring to be extracted.
stop Optional. A non-negative integer that is one position in the stringObject that is one more than the last character of the substring to be extracted. If this parameter is omitted, the returned substring will go to the end of the string.

Return value

A new string value contains a substring of stringObject whose content is from start The length of all characters up to stop-1 is stop minus start.

Description

The substring returned by the substring method includes the characters at start, but does not include the characters at end.
If start and end are equal, then this method returns an empty string (that is, a string with a length of 0).
If start is greater than end, then this method will exchange the two parameters before extracting the substring.
If start or end is negative, then it will be replaced by 0.

2. Substr method

Definition and usage

The substr method is used to return a A substring of the specified length starting at the specified position.

Syntax

stringObject.substr(start [, length])

Parameter Description
start Required. The starting position of the desired substring. The first character in the string has index 0.
length Optional. The number of characters that should be included in the returned substring.

Explanation

If start is a negative number, then start=str.length+start.
If length is 0 or negative, an empty string will be returned.
If this parameter is not specified, the substring will continue to the end of stringObject.

Small example:

var str = "0123456789";

alert(str.substring(0));------------"0123456789"
alert(str.substring(5));------------"56789"
alert(str.substring(10));-----------""
alert(str.substring(12));-----------""
alert(str.substring(-5));-----------"0123456789"
alert(str.substring(-10));----------"0123456789"
alert(str.substring(-12));----------"0123456789"
alert(str.substring(0,5));----------"01234"
alert(str.substring(0,10));---------"0123456789"
alert(str.substring(0,12));---------"0123456789"
alert(str.substring(2,0));----------"01"
alert(str.substring(2,2));----------""
alert(str.substring(2,5));----------"234"
alert(str.substring(2,12));---------"23456789"
alert(str.substring(2,-2));---------"01"
alert(str.substring(-1,5));---------"01234"
alert(str.substring(-1,-5));--------""

alert(str.substr(0));---------------"0123456789"
alert(str.substr(5));---------------"56789"
alert(str.substr(10));--------------""
alert(str.substr(12));--------------""
alert(str.substr(-5));--------------"56789"
alert(str.substr(-10));-------------"0123456789"
alert(str.substr(-12));-------------"0123456789"
alert(str.substr(0,5));-------------"01234"
alert(str.substr(0,10));------------"0123456789"
alert(str.substr(0,12));------------"0123456789"
alert(str.substr(2,0));-------------""
alert(str.substr(2,2));-------------"23"
alert(str.substr(2,5));-------------"23456"
alert(str.substr(2,12));------------"23456789"
alert(str.substr(2,-2));------------""
alert(str.substr(-1,5));------------"9"
alert(str.substr(-1,-5));-----------""

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