This JavaScript function called Array.prototype.mapUntil is like Array.prototype.map, but it only maps until a condition (predicate) is true.

mapUntil.js

Array.prototype.mapUntil = function(fn, predicate) {
  const arr = [];
  let done = false;
  this.forEach(el => {
    if (done) return arr;
    if (!predicate(el)) arr.push(fn(el));
    else done = true;
  });
  return arr;
};


// Example usage
const a = [1, 3, 5, 2, 3];

// map array multiplying all numbers by 2 until element === 5 is found
const a2 = a.mapUntil(i => i * 2, i => i === 5);

console.log(a2); // [2, 6]