Testing & Matching in JavaScript

// test() - Returns boolean
/\d+/.test("123")                 // true
/[a-z]+/.test("ABC")              // false

// match() - Returns array or null
"hello".match(/[aeiou]/g)         // ['e', 'o']
"hello".match(/(\w)(\w+)/)        // ['hello', 'h', 'ello']

// matchAll() - Returns iterator of all matches
const matches = "cat bat rat".matchAll(/(\w)at/g)
for (const match of matches) {
  console.log(match[0], match[1]) // 'cat' 'c', 'bat' 'b', etc
}

// search() - Returns index or -1
"hello world".search(/world/)     // 6
"hello world".search(/foo/)       // -1

// exec() - Returns match with details
const regex = /(\d{4})-(\d{2})/g
let match
while (match = regex.exec("2024-03-15 2025-04-20")) {
  console.log(match[0])  // "2024-03", "2025-04"
  console.log(match.index) // 0, 11
}