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Lookaheads use the ?= symbol. Lookbehinds use ?<=.
/(?<=Roger) Waters/
/(?<=Roger) Waters/.test('Pink Waters is my dog') //false
/(?<=Roger) Waters/.test('Roger is my dog and Roger Waters is a famous musician') //trueA lookbehind is negated using ?<!:
/(?<!Roger) Waters/
/(?<!Roger) Waters/.test('Pink Waters is my dog') //true
/(?<!Roger) Waters/.test('Roger is my dog and Roger Waters is a famous musician') //falseLessons in this unit:
| 0: | Introduction |
| 1: | Introduction |
| 2: | Anchoring |
| 3: | Match Items in Ranges |
| 4: | Matching a Range Item Multiple Times |
| 5: | Negating a Pattern |
| 6: | Meta Characters |
| 7: | Regular Expressions Choices |
| 8: | Quantifiers |
| 9: | Optional Items |
| 10: | Groups |
| 11: | Capturing Groups |
| 12: | Using match and exec Without Groups |
| 13: | Noncapturing Groups |
| 14: | Flags |
| 15: | Inspecting a Regex |
| 16: | Escaping |
| 17: | String Boundaries |
| 18: | Replacing |
| 19: | Greediness |
| 20: | Lookaheads |
| 21: | ▶︎ Lookbehinds |
| 22: | Unicode |
| 23: | Unicode Property Escapes |
| 24: | Examples |