JavaScript / ECMAScript

Duplicate Word in JS

Detects consecutive duplicate words using a backreference.

Try it in the JS tester →

Pattern

regexJS
\b(\w+)\s+\1\b   (flags: gi)

JavaScript / ECMAScript code

jsJavaScript
const re = new RegExp("\\b(\\w+)\\s+\\1\\b", "gi");
const input = "the the cat sat on the the mat";
const matches = [...input.matchAll(re)];
console.log(matches.map(m => m[0]));

Uses `String.prototype.matchAll` for global iteration (Node 12+ / all modern browsers).

How the pattern works

`\b(\w+)\b` captures a word. `\s+\1\b` matches whitespace followed by the same word (backreference `\1`). Case-insensitive.

Examples

Input

the the cat sat on the the mat

Matches

  • the the
  • the the

Input

no duplicates here

No match

—

Same pattern, other engines

Python (re)

Supported

See how this pattern looks (and behaves) in Python's stdlib `re` module.

Go (RE2)

See workaround

See how this pattern looks (and behaves) in Go's `regexp` package (RE2 engine).

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