Function is

src/utils/shallowEqual.js:18–29

* inlined Object.is polyfill to avoid requiring consumers ship their own * https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/is

(x, y)

 * https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/is
 */
function is(x, y) {
  // SameValue algorithm
  if (x === y) {
    // Steps 1-5, 7-10
    // Steps 6.b-6.e: +0 != -0
    // Added the nonzero y check to make Flow happy, but it is redundant
    return x !== 0 || y !== 0 || 1 / x === 1 / y;
  }
  // Step 6.a: NaN == NaN
  // eslint-disable-next-line no-self-compare
  return x !== x && y !== y;
}

/**
 * Performs equality by iterating through keys on an object and returning false