When you use `memo`, your component re-renders whenever any prop is not *shallowly equal* to what it was previously. This means that React compares every prop in your component with the previous value of that prop using the [`Object.is`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/is) comparison. Note that `Object.is(3, 3)` is `true`, but `Object.is({}, {})` is `false`.
### My component re-renders when a prop is an object, array, or function {/*my-component-rerenders-when-a-prop-is-an-object-or-array*/}
React compares old and new props by shallow equality: that is, it considers whether each new prop is reference-equal to the old prop. If you create a new object or array each time the parent is re-rendered, even if the individual elements are each the same, React will still consider it to be changed. Similarly, if you create a new function when rendering the parent component, React will consider it to have changed even if the function has the same definition. Avoid this by [simplifying props or memoizing props in the parent component](#minimizng-props-changes).
React compares old and new props by shallow equality: that is, it considers whether each new prop is reference-equal to the old prop. If you create a new object or array each time the parent is re-rendered, even if the individual elements are each the same, React will still consider it to be changed. Similarly, if you create a new function when rendering the parent component, React will consider it to have changed even if the function has the same definition. Avoid this by [simplifying props or memoizing props in the parent component](#minimizing-props-changes).
uthbees
2 years ago
GitHub