Use of substring and substr in js, jssubstringsubstr

Use of substring and substr in js, jssubstringsubstr
Usage of substring and substr in js

Substring is a substring between two subscripts, and substr is a substring of the specified length starting from the specified position.

The first parameters of both of them are the start point, the second parameter of substring is the end point, and the second parameter of substr is the length.

1. substring Method

The substring method is used to extract strings.Between two specified subscriptCharacter

Substring (start, end)

Start and end locations, index starting from scratch

Parameter description
Start is required. A non-negative integer that specifies the position of the first character of the substring to be extracted in the stringObject.
Optional. A non-negative integer is 1 more than the position of the last character of the substring to be extracted in the stringObject. If this parameter is omitted, the returned substring ends at the end of the string.

Return Value

A new string. The value of this string contains a substring of stringObject. Its content is all characters from start to stop-1, and its length is stop minus start.

Description

The substring returned by the substring method includes the start character, but not the end character.
If start and end are equal, this method returns an empty string (a string with a length of 0 ).
If start is greater than end, this method swaps the two parameters before extracting the substring.
If start or end is negative, it is replaced with 0.

 

2. substr Method

 

Definition and usage

The substr method is used to returnStart at specified positionOfLength.

Syntax

StringObject. substr (start [, length])

Parameter description
Start is required. The starting position of the required substring. The index of the first character in the string is 0.
Length is optional. The number of characters to be included in the returned substring.

Description

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

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 (-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 (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 ));-----------""

 

Refer:

Http://www.cnblogs.com/chinafine/archive/2009/02/26/1398771.html