JavaScript RegExp \n Metacharacter

The \n metacharacter in JavaScript regular expressions matches a newline character. It is used to identify line breaks in strings, enabling developers to process multi-line text effectively.

let regex = /\n/;
let str = "Hello\nWorld";
console.log(regex.test(str));

true

The pattern \n detects the presence of a newline character (\n) in the string.

Syntax:

/\n/

• \n: Matches a newline character in the input string.

Key Points

• Matches only newline characters (\n).
• Commonly used in parsing or validating multi-line text.
• Does not match other whitespace characters like spaces ( ) or tabs (\t).

Real-World Examples

1. Detecting a Newline

let regex = /\n/;
let str = "Line 1\nLine 2";
if (regex.test(str)) {
    console.log("Newline detected!");
} else {
    console.log("No newline found.");
}

Newline detected!

2. Splitting Text by Newlines

let str = "First line\nSecond line\nThird line";
let lines = str.split(/\n/);
console.log(lines);

[ 'First line', 'Second line', 'Third line' ]

This splits a multi-line string into an array of individual lines.

3. Replacing Newlines

let str = "Hello\nWorld";
let replaced = str.replace(/\n/g, " ");
console.log(replaced);

Hello World

The \n is replaced with a space, converting the string into a single line.

4. Counting Newlines in a String

let str = "Line 1\nLine 2\nLine 3";
let regex = /\n/g;
let count = (str.match(regex) || []).length;
console.log(count);

2

This counts the number of newline characters in the string.

5. Matching Specific Patterns Across Lines

let regex = /Hello\nWorld/;
let str = "Hello\nWorld";
console.log(regex.test(str));

true

Here, the regex explicitly matches the sequence Hello followed by a newline and World.

Common Patterns Using \n

• Match Strings with Newlines:

/Line 1\nLine 2/

• Replace Newlines with Spaces:

str.replace(/\n/g, " ");

• Count Newlines:

(str.match(/\n/g) || []).length;

• Split by Newlines:

str.split(/\n/);

• Remove All Newlines:

str.replace(/\n/g, "");

Limitations

Matches Only Newlines: It does not match other types of line terminators like \r. Use \r?\n for cross-platform newline matching.

Why Use \n Metacharacter?

• Multi-Line Parsing: Essential for processing text files, logs, or user inputs with line breaks.
• Efficient Line Handling: Enables developers to count, split, or manipulate strings based on newlines.
• Cross-Platform Compatibility: Use in combination with \r to handle newline variations between systems.

Conclusion

The \n metacharacter is a fundamental tool in regex for handling text spanning multiple lines. Its simplicity and effectiveness make it indispensable for string processing.

Recommended Links:

• JavaScript RegExp Complete Reference
• JavaScript Cheat Sheet-A Basic guide to JavaScript
• JavaScript Tutorial