JS: Regex Syntax. Character Class

By Xah Lee. Date: .
work in progress

Character class square brackets

Note, the pattern [syntax] is extremely complicated. Here we just document the most common use-cases.

when the square bracket pattern [syntax] is used with flag u or flag v, it has extended syntax.

Any character

[chars]

Any character between the brackets.

console.log(
  "cat cet cit cot cut".match(/c[aou]t/g),
);
// [ "cat", "cot", "cut" ]

Character range

[a-z]

char range from a to z. 

// character range

console.log(
  "Alice was.".match(/[a-z]+/g),
);
// [ "lice", "was" ]

// character range , digits.
console.log(
  "there are 3 cats.".match(/[0-9]+/g),
);
// [ "3" ]

With char class escape

contains_character_class_escape

word class in brackets

// using word class \w inside square brackets (redundant)
console.log(
 "ab-y42".match(/[\w]/g),
);
// [ "a", "b", "y", "4", "2" ]

unions of any char and range and char class escape

[mixed]
// a to g, 0 to 9
console.log(
 "ab-y42".match(/[a-g0-9]/g),
);
// [ "a", "b", "4", "2" ]
// a to g, 0 to 9, and y i j
console.log(
 "ab-iz42".match(/[a-g0-9yij]/g),
);
// [ "a", "b", "i", "4", "2" ]
// match word class \w plus hyphen
// when you have hyphen, best to put it in front, the avoid confusing with range syntax
console.log(
 "ab-y42".match(/[-\w]/g),
);
// [ "a", "b", "-", "y", "4", "2" ]

Negation

[^…]

Any char that's not one of the character in the brackets.