JavaScript .substr()

The .substr() method in JavaScript extracts a portion of a string, starting from a specified index position and extending for a specified number of characters. Indexing begins at zero. If a negative index is provided, it indicates the position from the end of the string, allowing extraction starting from the specified number of characters from the end.

Syntax

string.substr(start, length);

• start: The index position in the string where extraction begins. If negative, it counts from the end of the string.
• length: The number of characters to extract. It is an optional parameter. If omitted, the extraction continues to the end of the string.

Example

The example below shows the use of .substr() method in multiple ways:

// Extracting a portion of a string with a specified length.
var sentence1 = 'The Intro to JavaScript is fun to learn.';
console.log(sentence1.substr(4, 19));

// Extracting a portion of a string _without_ a specified length.
var sentence2 = 'The Intro to JavaScript is fun to learn.';
console.log(sentence2.substr(4));

// Extracting from the end of a string.
var sentence3 = 'The Intro to JavaScript is fun to learn.';
console.log(sentence3.substr(-27, 10));

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The above example prints the following output on the console:

Intro to JavaScript
Intro to JavaScript is fun to learn.
JavaScript

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Note: The .substr() method does not change the original string.