Mastering Substrings in Programming: A Beginner’s Guide

Unlock the Power of Substrings

When working with strings in programming, being able to extract specific parts of the string is a crucial skill. This is where the substring() method comes in, allowing you to extract a specified part of a string between start and end indexes.

Understanding the Syntax

The syntax of the substring() method is straightforward: str.substring(indexStart, indexEnd). Here, str is the original string, indexStart is the index of the first character to include in the returned substring, and indexEnd is the index before which to stop extraction (exclusive). If indexEnd is omitted, the method extracts till the end of the string.

Key Parameters to Keep in Mind

When using the substring() method, there are a few important parameters to keep in mind:

• Any argument value less than 0 is treated as 0.
• Any argument value greater than str.length is treated as str.length.
• Any NaN argument value is treated as 0.
• If indexStart is greater than indexEnd, the two arguments are swapped, meaning str.substring(a, b) becomes str.substring(b, a).

What to Expect from the Return Value

The substring() method returns a new string containing the specified part of the given string. Note that this method does not change the original string.

Putting it into Practice

Let’s take a look at an example of using substring() to extract a part of a string:

Example 1: Using substring

let str = "Hello World";
let extractedStr = str.substring(6, 11);
console.log(extractedStr); // Output: "World"


You can also use substring() to replace a part of a string:

Example 2: Replacing a substring within a string

let str = "Hello World";
let replacedStr = str.substring(0, 6) + "Universe";
console.log(replacedStr); // Output: "Hello Universe"


Related Methods

If you’re interested in learning more about string manipulation methods, be sure to check out the slice() method, which allows you to extract a section of a string and return it as a new string.