Analysis of substring and substr in JS _javascript techniques

Source: Internet
Author: User

1, substring method: to extract the string intermediary between the two specified subscript the character 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.


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.

2, substr method

Definitions and usage

The Substr method returns a substring of the specified length starting at the specified position.


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.


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.

Small example:

var str = "0123456789"; Alert (str.substring (0)),------------"0123456789" Alert (str.substring (5)),------------"56789" alert (str.substring (10)); -----------"" 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);---------" 0123456789 "Alert" (Str.substring (2,0)),----------"Alert" (Str.substring (2,2)),----------"" Alert str.substring (
2,5);----------"234" alert (str.substring (2,12)),---------"23456789" alert (str.substring);---------"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);------------ "0123456789" alert (STR.SUBSTR (2,0)),-------------"" Alert (Str.substr (2,2)),-------------"?" Alert (str.substr
)-------------"23456" alert (2,12),------------"23456789" alert (STR.SUBSTR)------------""  
 Alert (STR.SUBSTR ( -1,5));------------"9" Alert (STR.SUBSTR ( -1,-5));-----------""

The above is about JS in substring and substr method of simple introduction, I hope to help you learn.

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