generate.js

function getRandom(min, max) {
  return Math.round(Math.random() * (max - min) + min);
}

const generate = () => {
  const selected = []
  let max = 9
  let prev = null
  for (let i = 0; i < 4; i++) {
    const min = i === 0 ? 1 : 0
    let digit = getRandom(min, max)
    while (digit === prev || digit === prev + 1) {
      digit = getRandom(min, max)
    }
    selected.push(digit)
    prev = digit
  }
  // convert array to a 4 digit number
  const number = selected.reduce((total, i, idx) => total + (i * 10 ** (3 - idx)), 0)
  return number
}

const numberSet = {}
const generated = []
const count = 1000

while (generated.length < count) {
  num = generate()
  if (!numberSet[num]) {
    numberSet[num] = true
    generated.push(num)
  }
}

// console.log(generated.length)
console.log(generated)