react-fast-context

A simple library which lets you create and consume a context without every update to the context trigger an update to the current component.

Installation

npm i --save react-fast-context

Usage

The API mirrors the built in React context API, but with the extra shouldUpdate option, which allows you to decide if an update to the value should trigger an update to the component, similar to shouldComponentUpdate.

Create a context

Takes the same generic type and default value argument as createContext, but returns a FastContext.

import { createFastContext } from 'react-fast-context';

export const myContext = createFastContext<{ foo: string, bar: number }>({
    foo: "",
    bar: 0,
});

Add the provider

Again, this is no different to a regular react context

export const MyProvider = ({ children }) => (
    <myContext.Provider value={{ foo: "asdf", bar: 20 }}>
        {children}
    </myContext.Provider>
)

Using a consumer

Like a regular consumer, except the shouldUpdate prop must be supplied to determine whether to update or not. In this case, ignore updates to bar as it isn't used.

export const MyComponent = () => {
    return (
        <myContext.Consumer shouldUpdate={(oldValue, newValue) => oldValue.foo !== newValue.foo}>
            {({ foo }) => (
                <>
                    Value: {foo}
                </>
            )}
        </myContext.Consumer>
    );
};

Use the hooks

You can use useFastContext, which is like the normal useContext, but requires a second argument to determine updates:

export const useFoo = () => {
    const { foo } = useFastContext(myContext, (oldValue, newValue) => oldValue.foo !== newValue.foo);

    return foo;
}

Or you can use useCurrentContext, which returns the context value wrapped in a ref object, so will never trigger a re-render, but can always be used to access the latest context value.

export const Component = () => {
    const ref = useCurrentContext(myContext);

    return <Child onEvent={() => {
        console.log(ref.current.foo)
    }} />
}