1. Substring method:Used to extract substring(start, end) characters in a string between two specified subscripts
Start and end positions, index starting from zero
Parameters Description
start A non-negative integer that specifies the position of the first character of the substring to be extracted in stringObject.
stop Optional. A non-negative integer has one more position in stringObject than the last character of the substring to be extracted. If this parameter is omitted, the returned substring will continue to the end of the string.
Return value
A new string whose value contains a substring of stringObject whose content is all characters from start to stop-1, with a length of stop minus start.
illustrate
The substring method returns a substring including the characters at start, but not the characters at end.
If start and end are equal, then the method returns an empty string (that is, a string of length 0).
If start is larger than end, the method will swap these two parameters before extracting the substring.
If start or end is negative, then it will be replaced with 0.
2. Substr method
Definition and usage
The substr method returns a substring of the specified length starting from the specified position.
grammar
(start [, length ])
Parameters Description
start Required. The starting position of the required substring. The index of the first character in the string is 0.
length optional. The number of characters that should be included in the returned substring.
illustrate
If start is negative, start=+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 the stringObject.
Small examples:
var str = "0123456789"; alert((0));------------"0123456789" alert((5));------------"56789" alert((10));-----------"" alert((12));-----------"" alert((-5));-----------"0123456789" alert((-10));----------"0123456789" alert((-12));----------"0123456789" alert((0,5));----------"01234" alert((0,10));---------"0123456789" alert((0,12));---------"0123456789" alert((2,0));----------"01" alert((2,2));----------"" alert((2,5));----------"234" alert((2,12));---------"23456789" alert((2,-2));---------"01" alert((-1,5));---------"01234" alert((-1,-5));--------"" alert((0));---------------"0123456789" alert((5));---------------"56789" alert((10));--------------"" alert((12));--------------"" alert((-5));--------------"56789" alert((-10));-------------"0123456789" alert((-12));-------------"0123456789" alert((0,5));-------------"01234" alert((0,10));------------"0123456789" alert((0,12));------------"0123456789" alert((2,0));-------------"" alert((2,2));-------------"23" alert((2,5));-------------"23456" alert((2,12));------------"23456789" alert((2,-2));------------"" alert((-1,5));------------"9" alert((-1,-5));-----------""
The above is a brief introduction to the methods of substring and substr in js. I hope it will be helpful to everyone's learning.