JavaScript String charCodeAt()

// string definition
const greeting = "Good morning!";

// UTF-16 code unit of character at index 5
let result = greeting .charCodeAt(5);

console.log(result);

// Output: 109

charCodeAt() Syntax

The syntax of the charCodeAt() method is:

str.charCodeAt(index)

Here, str is a string.

charCodeAt() Parameters

The charCodeAt() method takes a single parameter:

• index - An integer between 0 and (str.length - 1).

Note: The str.length returns the length of a given string.

charCodeAt() Return Value

• Returns a number representing the UTF-16 code unit value of the character at the given index.

Example 1: Using charCodeAt() Method

const greeting = "Good morning!";

// UTF-16 code unit of character at index 5
let result1 = greeting .charCodeAt(5);

console.log(result1);

// UTF-16 code unit of character at index 5.2
let result2 = greeting .charCodeAt(5.2);

console.log(result2);

// UTF-16 code unit of character at index 5.9
let result3 = greeting.charCodeAt(5.9);

console.log(result3);

Output

109
109
109

In the above example, we are using the charCodeAt() method to access the UTF-16 code unit of the character at index 5.

Since the character present at index 5 is "m", the method returns UTF-16 code unit of "m".

Similarly, for the non-integer index 5.2 and 5.9, the numbers are converted to nearest integer value i.e. 5, so the method again returns UTF-16 code unit of "m" i.e. 109.

Example 2: charCodeAt() Method for Index Out of Range

const greeting = "Good morning!";

// passing index greater than length of string 
let result3 = greeting.charCodeAt(18);

console.log(result3);

// passing non-negative index value
let result4 = greeting.charCodeAt(-9);

console.log(result4);

Output

NaN
NaN

In the above example, we have created a string "Good morning!".

Here, both the code greeting.charCodeAt(18) and greeting.charCodeAt(-9) returns NaN because both indexes 18 and -9 are not present in the given string.

Example 3: charCodeAt() with Default Parameter

const greeting = "Good morning!";

// without passing parameter in charCodeAt() 
let result1 = greeting.charCodeAt();

console.log(result1);

// passing 0 as  parameter
let result2 = greeting.charCodeAt(0);

console.log(result2);

Output

71
71

In the above example, since we have not passed any parameter in charCodeAt(), the default value will be 0.

So the method returns UTF-16 code unit of character at index 0 i.e. 71.

Recommended Reading: JavaScript String fromCharCode()