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How to Split a String into Substrings in JavaScript

William Shakespeare

Feb 09, 2025 am 10:59 AM

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    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>JavaScript String Splitting: substring() vs. split()</title>
</head>
<body>
    <h1 id="JavaScript-String-Splitting-substring-vs-split">JavaScript String Splitting: `substring()` vs. `split()`</h1>

    <p>JavaScript offers two primary methods for dividing strings into substrings:  `substring()` and `split()`.  Each serves a distinct purpose.</p>

    <h2 id="substring">`substring()`</h2>
    <p>The `substring()` method extracts a portion of a string based on starting and ending indices. It's ideal for retrieving a single substring from a known position within the string.</p>

    <p><strong>Syntax:</strong> <code>string.substring(startIndex, endIndex)</code></p>
    <ul>
        <li><code>startIndex</code>: The index of the first character to include (0-based).</li>
        <li><code>endIndex</code> (optional): The index *after* the last character to include. If omitted, the substring extends to the end of the string.</li>
    </ul>

    <p><strong>Example:</strong></p>
    <pre class="brush:php;toolbar:false"><code>
const str = "Hello, world!";
const sub = str.substring(7, 12); // Extracts "world"
console.log(sub); // Output: "world"

Often, you'll use `indexOf()` to dynamically determine the start or end indices.

`split()`

The `split()` method divides a string into an array of substrings based on a specified separator. This is perfect for handling strings containing lists of items delimited by a character (e.g., comma-separated values).

Syntax: string.split(separator, limit)

separator: The character or string used to divide the string.
limit (optional): The maximum number of substrings to return.

Example:

<code>
const csv = "apple,banana,cherry";
const fruits = csv.split(","); // Splits at each comma
console.log(fruits); // Output: ["apple", "banana", "cherry"]
    </code>

Key Differences

Feature	`substring()`	`split()`
Output	Substring (string)	Array of substrings
Purpose	Extract a portion at specific indices	Split into multiple substrings based on a separator
Index-based	Yes	No (separator-based)

When to Use Each Method

Use `substring()` when you need to extract a single, continuous piece of text from a known position within the string.
Use `split()` when you need to break a string into multiple parts based on a delimiter, such as commas, spaces, or other characters.

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