The function object equals only to itself. You gain no performance benefits but also run for naught the comparison function. Because props comparison almost always returns false, React performs the diff of previous and current render results.Invokes the comparison function to determine whether the previous and next props are equal.In this case, memoization doesn't provide benefits.Įven if you wrap such a volatile component in mo(), React does 2 jobs on every rendering: Imagine a component that usually renders with different props. Extend PureComponent class or define a custom implementation of shouldComponentUpdate() method if you need memoization for class-based components. While possible, wrapping class-based components in mo() is undesirable. Performance-related changes applied incorrectly can even harm performance. Use the following rule of thumb: don't use memoization if you can't quantify the performance gains. If the component isn't heavy and usually renders with different props, most likely you don't need mo(). The more often the component renders with the same props, the heavier and the more computationally expensive the output is, the more chances are that component needs to be wrapped in mo().Īnyways, use profiling to measure the benefits of applying mo(). This improves the performance of MovieViewsRealtime component. The functional component Movie is wrapped in mo():Īs long as title and releaseDate props are the same, React skips rendering MemoizedMovie. Before the next render, if the new props are the same, React reuses the memoized result skipping the next rendering. When a component is wrapped in mo(), React renders the component and memoizes the result. But you can speed up the process under some circumstances. If the render results are different, React updates the DOM.Ĭurrent vs previous render results comparison is fast. When deciding to update DOM, React first renders your component, then compares the result with the previous render. Plus I'll describe some useful memoization tips you should be aware of. This post describes the situations when mo() improves the performance, and, not less important, warns when its usage is useless. When mo() wraps a component, React memoizes the rendered output of the wrapped component then skips unnecessary renderings. To improve user interface performance, React offers a higher-order component mo(). A UI response delay of fewer than 100 milliseconds feels instant to the user but a delay between 100 and 300 milliseconds is already perceptible. Users enjoy fast and responsive user interfaces (UI).
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