JavaScript substring and substr usage differences

Source: Internet
Author: User

Substring method

The substring method is used to extract characters from the string mediation between the two specified subscripts

SUBSTRING (start,end)

Start and end positions, zero-based index

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

return value

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

Description

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

Cases

The code is as follows Copy Code


var stringobject = "Hello world!";
Alert (stringobject.substring (3)); Lo world!
Alert (stringobject.substring (3,stringobject.length)); Lo world!
Alert (stringobject.substring (3,7)); Lo W, Space also counted [l][o][][w]


2 if the startindex and endindex are equal, the empty string is returned. If the startindex is larger than the Endindex, swap two parameters before extracting the substring. i.e. stringobject.substring (Startindex,endindex) is equivalent to stringobject.substring (Endindex,startindex)

The code is as follows Copy Code


var stringobject = "Hello world!";
Alert (stringobject.substring (3,3)); Empty string
Alert (stringobject.substring (3,7)); Lo W
Alert (stringobject.substring (7,3)); Lo W


substr Method


Definitions and usage

The Substr method returns 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.

The code is as follows Copy Code
var stringobject = "Hello world!";
Alert (STRINGOBJECT.SUBSTR (3)); Lo world!
Alert (STRINGOBJECT.SUBSTR (3,stringobject.length)); Lo world!
Alert (STRINGOBJECT.SUBSTR (3,4)); Lo W


Example:

The code is as follows Copy Code

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

SUBSTR () can be used instead of substring (), which shows that stringobject.substr (3,4) is equivalent to Stringobject.substring (3,7) in the code above

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