JavaScript String startsWith

The startsWith() method is a built-in method in JavaScript that is used to determine whether a string starts with a specified substring. It returns true if the string starts with the specified substring, and false otherwise.

Here’s the syntax of the startsWith() method:

str.startsWith(searchString[, position])

• searchString: The substring to search for at the start of the string.
• position (optional): The position in the string at which to start the search. Defaults to 0.

Here’s an example usage of the startsWith() method:

const str = 'Hello, world!';

console.log(str.startsWith('Hello')); // Output: true
console.log(str.startsWith('hello')); // Output: false
console.log(str.startsWith('world', 7)); // Output: true

In this example, we have a string str that contains the text “Hello, world!”. We use the startsWith() method to check if the string starts with different substrings.

• The first startsWith('Hello') call returns true because the string str starts with the substring “Hello”.
• The second startsWith('hello') call returns false because the startsWith() method performs a case-sensitive comparison, and the string str does not start with the substring “hello” (note the lowercase ‘h’).
• The third startsWith('world', 7) call returns true because the search starts at index 7, and the remaining part of the string starting from that index is “world”.

The startsWith() method is particularly useful when you need to perform string prefix checks or pattern matching in JavaScript.