Description

The JavaScript String property length returns the number of characters (or length) in a string.

Syntax

The property length has the below syntax, where str is a string.

str.length

Parameters

The property length doesn't take any properties.

Result

The property length returns the number of characters in a string.

Example 1: Using the Property

The property simply returns the size of a string.

var str = "Hello World!";

// Finding length of a string
document.write(str.length);         // Prints: 12

// Finding length of a blank string
document.write("".length);          // Prints: 0

// Finding length of a null value
document.write(null.length);       // Returns error

Output:

12
0

Example 2: Finding Length of a Null

The fromIndex is used to find the position from where the backward search must perform within the string.

// Finding length of a null value
document.write(null.length);       // Returns error

Output:

Uncaught TypeError: Cannot read properties of null (reading 'length')

Example 3: Length Property is Read-Only

The property length is a read-only property and we cannot assign a value to overwrite a string length.

var str = "Hello World!";

// Finding length of a string
document.write(str.length);         // Prints: 12

str.length = 5;

// Finding length of a string
document.write(str.length);         // Prints: 12

Output:

12
12

Example 4: Using Length Property to Read Characters of a String

We can use the property length to read the ending characters of a string.

var str = "Hello World!";

// Reading the last character of a string
document.write(str[str.length - 1]);         // Prints: !

// Reading the second last character of a string
document.write(str[str.length - 2]);         // Prints: d

Output:

!
d

Overall

The JavaScript String property length returns the number of characters in a string.

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