CODEWITHSUNDEEP
regex
PoseLab
PoseLab

Reputation: 1899

Regex repeated words on the same line

What is the regular expression to find words that are repeated on the same line?

I've tried some expressions that I found on Stack Overflow, such as this, but none is working correctly.

The result I want to achieve:

Enter image description here

Upvotes: 4

Views: 15087

Answers (4)

bart
bart

Reputation: 7767

This regex will do to find which words you want to highlight. (The example is in JavaScript, and it is easy to test in the browser's JavaScript console.)

s = "It's a foo and a bar and a bar and a foo too.";
a = s.match(/\b(\w+)\b(?=.*\b\1\b)/g);

This returns an array of words, possibly multiple times for the same word.

Next you can do this:

re = new RegExp('\\b(' + a.join('|') + ')\\b', 'g');

And that should suffice to highlight all occurrences:

out = s.replace(re, function(m) { return '<b>' + m + '</b>' });

Upvotes: 20

Aryeetey Solomon Aryeetey
Aryeetey Solomon Aryeetey

Reputation: 5836

If you want to find multiple words right after each other, for example,

Sam went went to to to his business

you can use this regex:

s = "Sam went went to to to his business";
a = s.match(/\b(\w+)(\s\1)+\b/g);

Upvotes: 1

Just Me
Just Me

Reputation: 1053

You can use this regex to find consecutive words, next to each other.

For example: "My name is Prince Prince, and I love cats." The regex below will find Prince Prince. It is the simplest version.

(\w+)(\s\1)+

Upvotes: -1

Gusdor
Gusdor

Reputation: 14334

In the absence of a sample string, lets use a test case and a few examples of how to can achieve this.

String

My name is James and James is my name

Regex

^(James)$

Group 1 (0 is generally the full match string and will likely not have a capture count) is captured twice. This means that the word is repeated. Some logic is required in the the tool you are using to execute your regex in order to decide how if you are interested in the 'word'.

Using the same string, consider this regex

(?<=James.*)(James)

This will detect the word James ONLY if it is proceeded by 'James' followed by any character. Depending on your engine, the '.' (period) should match any character that is not a newline by default. This confines the search to a single line.

Note the limitation of having to specify the word exactly. I am not sure how to get around this.

EDIT Try this, it's a doozy..

(?<=^|\s+\1\s+.*)\s+(\w+)

Using positive lookbehind (as in example 2) we detect 'whole words' that match our current group. A whole word is defined as:

  • Our current word
  • Proceeded by at least 1 space character or at the start of a line
  • Followed by at least 1 space

Further, the match we are on must be a standalone word (preceeded by at least one space character).

As far as results are concerned, each match will be a repeated word.

Upvotes: 0

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