Detailed explanation of substring and substr methods in JS

1. substring method

Definition and usage:
The substring method is used to extract a string between two specified subscripts. characters between.

Syntax:
stringObject.substring(start,end)

Parameter Description:
start Required. A nonnegative integer that specifies the position in stringObject of the first character of the substring to be extracted.
end Optional. A nonnegative integer that is one position in the stringObject that is one more than the last character of the substring to be extracted. If this parameter is omitted, the returned substring will go to the end of the string.

Return value:
A new string value contains a substring of stringObject, whose content is all characters from start to end-1 , its length is end minus start.

Description: The substring returned by the
substring method includes the characters at start, but does not include the characters at end.
If start and end are equal, then this method returns an empty string (that is, a string with a length of 0).
If start is greater than end, then this method will exchange the two parameters before extracting the substring.
If start or end is negative, then it will be replaced with 0.

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(-1,5));---------"01234"
alert(str.substring(-1,-5));--------""

2. substr method

Definition and usage:
The substr method is used to return a substring of the specified length starting from the specified position.

Syntax:
stringObject.substr(start [, length])

Parameter Description:
start Required. The starting position of the desired substring. The first character in the string has index 0.
length Optional. The number of characters that should be included in the returned substring.

Description:
If length is 0 or a negative number, an empty string will be returned.
If this parameter is not specified, the substring will continue to the end of stringObject.

Example:
var str = "0123456789";

##alert(str.substr(0) );---------------"0123456789"alert(str.substr(5));---------------"56789 "
alert(str.substr(10));--------------""
alert(str.substr(12));------- -------""
alert(str.substr(-5));--------------"0123456789"
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));----------------"01234"
alert(str.substr(-1,-5));--------- --""

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