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JavaScript RegExp dotAll Property

Last Updated : 5 Aug, 2025

The dotAll property in JavaScript regular expressions determines whether the 's' (dotAll) flag is enabled. This flag modifies the behaviour of the dot (.) metacharacter, allowing it to match any character, including line terminators like \n, \r, and others. Without the s flag, the dot (.) matches any character except line breaks.

The dotAll property is a read-only Boolean that reflects whether the s flag is active in a given regular expression.


Output
false
false
true
true
  • Without s flag: The dot (.) does not match line breaks, so "a\nb" fails to match.
  • With s flag: The dot (.) matches line breaks, allowing "a\nb" to match successfully.

Syntax

regex.dotAll

Key Points

  • Read-Only: Indicates whether the s flag is present in the regex.
  • Enhanced Matching: When the s flag is set, the dot (.) matches all characters, including line terminators.
  • Default Behavior: By default, dotAll is false unless explicitly enabled with the s flag.

Real-World Examples of the dotAll Property

1. Matching Multiline Strings


Output
true

With the s flag, the dot (.) matches the newline character, allowing the regex to match the entire "Hello\nWorld!" string.

2. Extracting Text Across Lines


Output
true
Start
Middle
End

The .* pattern, combined with the s flag, matches everything from "Start" to "End", including newlines.

3. Simple Multiline Match


Output
true

4. Finding Content Between Tags


Output
<div>
 Content
</div>

5. Matching Entire Multiline Blocks


Output
true

6. Comparing dotAll and Multiline (m) Flags

  • s (dotAll): Allows . to match newlines.
  • m (multiline): Modifies ^ and $ to match the start and end of each line.

Output
true
true

Why Use the dotAll Property?

  • Simplified Matching: Avoid the need for explicit patterns like [\s\S] to match line terminators.
  • Cleaner Regex: Makes regular expressions more readable and concise for multiline data.
  • Versatile Use: Ideal for processing logs, HTML, or any content with potential line breaks.

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