Strings in JavaScript (OCR A Level Computer Science)

Strings in JavaScript

A string is a sequence of characters enclosed in single quotes (') or double quotes ("). Strings are widely used for representing and manipulating text-based data.

Creating strings

• Strings can be created in JavaScript by enclosing text within quotes:

const message = 'Hello, world!';
const name = "John Doe";

String length

• To find the length of a string, use the length property

• The length property returns the number of characters in a string:

const message = 'Hello, world!';
console.log(message.length);

// Output: 13

• In this example, the length property is used to determine the number of characters in the message string

Substring extraction

• To extract a portion of a string, use the substring() method

• The substring() method takes two parameters: the starting index and the ending index (optional)

• A new string is returned containing the characters within the specified range:

const message = 'Hello, world!';
const substring = message.substring(0, 5);
console.log(substring);

// Output: Hello

• In this example, the substring() method is used to extract the characters from index 0 to index 5 (exclusive) from the message string, resulting in the substring 'Hello'

• By omitting the second parameter, the substring() method will extract the characters from the starting index to the end of the string:

const message = 'Hello, world!';
const substring = message.substring(7);
console.log(substring);

// Output: world!

• Here, the substring() method extracts the characters from index 7 to the end of the message string, resulting in the substring 'world!'