Usage of substring and substr in JS

The

substring method is used to extract the characters in the string between two specified subscripts

substring(start,end)

Start and end positions, zero-based index

Parameter Description

start Required. A nonnegative integer that specifies the position in stringObject of the first character of the substring to be extracted.
stop 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. The string value contains a substring of stringObject. Its content is all the characters from start to stop-1, and its length is stop minus start.

Explanation

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 these two parameters before extracting the substring.

If start or end is negative, then it will be replaced by 0.

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.

Explanation

If start is a negative number, then start=str.length+start.

If length is 0 or negative, an empty string will be returned.

If this parameter is not specified, the substring will be continued to the end of stringObject.

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));--------""
alert(str.substr (0));---------------"0123456789"
alert(str.substr(5));---------------" 56789"
alert(str.substr(10));--------------""
alert(str.substr(12));---------- ----""
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));----------""