JavaScript String.charCodeAt() Method

1. Syntax of JavaScript string.charCodeAt():
2. Example Codes: Find the ASCII of Character in a String Using JavaScript string.charCodeAt() Method
3. Example Codes: Get the Unicode of a Character With JavaScript string.charCodeAt() Method
4. Example Codes: Out of Bound Parameter in JavaScript string.charCodeAt() Method

The string.charCodeAt() is a JavaScript method that gives the UTF-16 Unicode unit of the specified i-th character of the calling string object. The index of the i-th character is passed as a parameter to the method.

Syntax of JavaScript string.charCodeAt():

string.charCodeAt(i);

Parameter

Return

The JavaScript string.charCodeAt() method returns the UTF-16 unit code of the specified i-th character of the string as an integer-type object. If the i parameter of the string.charCodeAt() method is not in the range of 0 to string length, it will return NaN.

1. The UTF-16 unit code is a 16-bit number between 0 and 65535. The string.charCodeAt() will always return an integer value less than 65535.
2. When a Unicode value (values greater than 0xFFFF), the method returns the first component of a pair of the code.

Example Codes: Find the ASCII of Character in a String Using JavaScript string.charCodeAt() Method

The first 128 UTF-16 multi-byte codes of characters are the same as the ASCII single-byte codes of those characters. If the returned number is between 0 and 128, then it is the ASCII of that character.

const string = 'welcome to hello world';
const i = 4;

console.log(`The ASCII code of character at index ${i} in the string is ${string.charCodeAt(i)}.`);

Here, i is the position of the character. In the above example, the string.charCodeAt() method returns an integer number that indicates the UTF-16 code of the 4th character of the string.

Output:

The ASCII code of character at index 4 in the string is 111.

As the character at index 4 of the string is o, the string.charCodeAt() method returns the Unicode of o.

Example Codes: Get the Unicode of a Character With JavaScript string.charCodeAt() Method

The string.charCodeAt() can also be used to get the Unicode of a character in a string.

const character='a';

console.log(character.charCodeAt());
console.log(character.charCodeAt(0));

Here, passing the i parameter as 0 or passing no parameter to the method gives a similar result as the JavaScript string.charCodeAt() parameter is set to 0 at default.

Output:

97
97

Example Codes: Out of Bound Parameter in JavaScript string.charCodeAt() Method

In this example, to get the Unicode value for a character at a certain point, we called the charCodeAt() method of the s_string variable.

var s_string = 'DelftStack';

console.log(s_string.charCodeAt(0));    //D
console.log(s_string.charCodeAt(1));    //e
console.log(s_string.charCodeAt(2));    //l
console.log(s_string.charCodeAt(3));    //t
console.log(s_string.charCodeAt(-4));

Output:

68
101
108
102
NaN

The console prints NaN as the i parameter was out of range.