JavaScript Substring

Substring() , Substr() and Slice()

In Javascript, you can extract the portion of a string from a larger string through one of following methods. They are string.substring(), string.substr() and string.slice().

Substring()

Javascript string substring() method extracts the characters from a larger string based on character indexes and returns the new sub string.

Syntax

string.substring(startIndex,endIndex);

startIndex : An integer value representing where to start the extraction.

endIndex: An integer value representing the position up to end the extraction, the endIndex value is not included in the returned substring. (that is endIndex value -1). This endIndex is optional, if it is omitted, the method will extract it extracts the rest of the string from startIndex.

	var str = "This is a string";
	str.substring(10,16);

The above code will return “string” that is it extract from the position 10 and upto 16 (16-1, because endIndex is not included).

More Javascript substring examples

	var str = "This is a string";
	str.substring(16,10);

The above code will return “string”, because the startIndex is greater than endIndex, it will swap the values.

	var str = "This is a string";
	str.substring(15,16);

It will return only one character, that is “g”.

	var str = "This is a string";
	str.substring(5);

It will return “is a string”, it will extract from the position 5 to end of the string because endIndex is omitted.

	var str = "This is a string";
	str.substring(0,4);

It will return “This” , it will extract first 4 characters because start index is 0.

	var str = "This is a string";
	str.substring(-4);

It will return “This is a string”, if the startIndex is less than 0 (zero), it will extract from the index position 0 (zero).

Substr()

Javascript string substr() method accept two arguments and return a new string. The first argument is the index position and second argument is length. The substr() method extract a new string from the start index position and number of characters specified in the length parameter.

Syntax

string.substr(startIndex, length);

example

	var str = "This is a string";
	str.substr(10,6);

It will return “string”, that is it extract from the position 10 and extract 6 characters.

More substr() examples

	var str = "This is a string";
	str.substr(5);

It will return “is a string” , it will extract from the position 5 and up to end of the string, because the length argument is missing.

Slice()

Javascript String slice() method extracts the characters from startIndex to endIndex

Syntax

string.slice(startIndex,endIndex);

startIndex : An integer value representing where to start the extraction.

endIndex: An integer value representing the position up to end the extraction, the endIndex value is not included in the extracted string. (that is endIndex value -1). This endIndex is optional, if it is omitted, the method will extract it extracts the rest of the string from startIndex.

	var str = "This is a string";
	str.slice(10,16);

It will return “string”, that is , extract from the startIndex position and upto endIndex position -1 (endIndex value is not included).