Lessons · Regex · backreferences
The same thing again
\1 matches whatever group 1 captured, so (\w)\1 is a doubled letter.
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What it is for
Repeated words, matching open and close quotes, duplicated fields.
How to think about it
Must this be the SAME thing as before? Capture the first occurrence, then refer back with \N where the repeat should be.
Worked example
pattern: (['"]).*?\1Whatever quote opened must close.
text: say 'hi' nowMatches 'hi'.
text: say 'hi" nowNo match: mismatched quotes.
Your turn
Two identical digits in a row.
(\d)
Test a pattern against real text
The trap
In a replacement string the syntax is $1, not \1, in JavaScript.
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