The usage of substring and substr in JS

The usage of substring and substr in JS

SUBSTRING is a substring between two subscripts, substr is a substring of the specified length at the beginning of the specified position.

The first parameter of both is the starting point, the second argument 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 characters between two specified subscripts in a string

SUBSTRING (start,end)

Start and end position, zero-based index

Parameter description
Start Required. A nonnegative integer that specifies the position of the first character of the substring to be extracted in the stringobject.
Stop is optional. A nonnegative integer that is 1 more than the last character of the substring to extract in Stringobject. If this argument is omitted, the returned substring continues until the end of the string.

return value

A new string value that contains a substring of stringobject whose contents are all characters from start to stop-1, with a length of stop minus start.

Description

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

2.substr method

Definition and usage

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

Grammar

Stringobject.substr (start [, length])

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

Description

If start is a negative number, then Start=str.length+start.
If length is 0 or negative, an empty string is returned.
If this argument is not specified, the substring continues to the end of the stringobject.

Example:
var str = "0123456789";

Alert (str.substring (0));------------"0123456789"
Alert (str.substring (5));------------"56789"
alert (str.substring);-----------""
alert (str.substring);-----------""
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);--------------""
alert (STR.SUBSTR);--------------""
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));-----------""

Reference:

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

The usage of substring and substr in JS