RegexpGarden

Garden Text Representation

let garden = "Rose\tRosemary\tRose\tRose\tPrimrose\t

Rosemary\tRose\tRose\tRose\tRosemary";

Code Editor
Log

123456

garden = garden

.replace(//gi, "Blackberry");

Lesson 33 / 42

Lesson task •

The rose should be replaced with blackberry if it is followed directly by rosemary or by another rose that should be replaced

Positive lookahead

(?=...) again

/x(?=y)/ matches "x" only if it is directly followed by "y"

Positive lookaheads can include nested capturing and non-capturing groups witch allows to form complex conditions. Let's say we need to replace with "bar" the first "foo" in the sequence of three "foo" followed up directly by "42":

1234

console.log("foo foo foo 42".replace(/foo(?=(\s*foo\s*){2}42)/gi, "bar")) // bar foo foo 42

console.log("foo foo 42".replace(/foo(?=(\s*foo\s*){2}42)/gi, "bar")) // foo foo 42

console.log("foo 42".replace(/foo(?=(\s*foo\s*){2}42)/gi, "bar")) // foo 42

console.log("foo foo foo foo 42".replace(/foo(?=(\s*foo\s*){2}42)/gi, "bar")) // foo bar foo foo 42