Jest Expect Polyfill

function expect(actualNumber) {
  return {
    toBe: function (expectNumber) {
      return Object.is(actualNumber, expectNumber);
    },

    not: {
      toBe: function (expectNumber) {
        return !Object.is(actualNumber, expectNumber);
      },
    },
  };
}

console.log(expect(3).toBe(3)); // true
console.log(expect(3).toBe(4)); // false
console.log(expect(3).not.toBe(4)); // true
console.log(expect(3).not.toBe(3)); // false