@retsam/react-ko v0.4.0

A library for allowing Knockout observables to be used with React components. Knockout's observable system is very similar to MobX, so in practice this is very much like using mobx-react.

This intended as a migration path for legacy Knockout codebases - the knockout html template engine can be replaced with React templates, while leaving the core Knockout logic intact, allowing for an incremental migration path to React.

This library provides utilities for allowing React components to rerender, driven by observables (like MobX), and a bindingHandler to bridge from ko templates to react components. (There is not currently any provided mechanism for the reverse: rendering knockout templates from react components)

API

Hooks

useComputed

A hook version of ko.pureComputed, wraps a function, returns the value of evaluating the function, and recomputes the function whenever any observables that are read by the function change.

interface FullNameProps {
    firstName: KnockoutObservable<string>,
    lastName: KnockoutObservable<string>
}

// Re-renders if either firstName or lastName change
const Greeter = ({firstName, lastName}: FullNameProps) => useComputed(() => (
    <span>
        Hello, {firstName()} {lastName()}
    </span>
));

Can largely be used as a drop-in replacement for the observe HOC.

useObservable

Reads and subscribes to an observable - if the observable's value changes the component re-renders:

interface FullNameProps {
    firstName: KnockoutObservable<string>,
    lastName: KnockoutObservable<string>
}

// Re-renders only if firstName changes
const Greeter = ({firstName, lastName}: FullNameProps) => {
    const [fName] = useObservable(firstName)
    return (
        <span>
            Hello, {fName} {lastName()}
        </span>
    );
}

Higher Order Component - observe

A Higher Order Component which wraps a component such that any observables that are read during the render function will cause the component to rerender.

interface FullNameProps {
    firstName: KnockoutObservable<string>,
    lastName: KnockoutObservable<string>
}

// Re-renders if either firstName or lastName change
const Greeter = observe(({firstName, lastName}: FullNameProps) => (
    <span>
        Hello, {firstName()} {lastName()}
    </span>
));

The implementation details of observe however, are somewhat ugly, and it should be considered deprecated in favor of the hooks API.

Knockout bindingHandler reactComponent

Used to bridge from "knockout world" into React world, useful for incrementally migrating from knockout templates to React components.

<div data-bind="
    reactComponent: {
        component: MyComponent,
        props: {prop: 'propValue'}
    }
"><!-- MyComponent will render here --></div>

Must be registered in ko.bindingHandlers, can be done by calling the exported register function.

Shorthand syntax

If registerShorthandSyntax is called, knockout preprocessNode logic will be registered which allows the previous example to be written as:

<!-- react: MyComponent {
    prop: 'propValue'
} -->

This will insert a div and render MyComponent inside it.