@hookstate/core

@hookstate/core

The flexible, fast and extendable state management for React that is based on hooks.

Modern alternative to Redux, Mobx, Formik without boilerplate but with impressive performance and predictable behavior.

Browse demos and code samples to see what it can do and learn it in few minutes.

Any questions? Just ask by raising a github ticket.

Why Hookstate

• Concise, pragmatic but flexible API. Very easy to learn. See "Getting Started" code sample.
• Incredible performance based on unique method for tracking of used/rendered and updated state segments. See the performance demo.
• First-class Typescript support. Complete type inferrence for any complexity of structures of managed state data. Full intellisense support tested in VS Code.
• Plugin system enables custom extensions, with several standard plugins available.
• Tiny footprint: 2.13KB gziped. No external dependencies, except React.

Installation

npm install --save @hookstate/core
# OR
yarn add @hookstate/core

API Documentation

createStateLink

This function creates a reference to a global state. The first argument is the initial value to assign to the state. For example (see it running):

interface Task { name: string; priority?: number }
const initialValue: Task[] = [{ name: 'First Task' }];
const stateRef = createStateLink(initialValue);

You can attach various plugins using with method of the state reference.

You can also wrap the state reference by your custom state access interface using the second transform argument.

useStateLinkUnmounted

This function opens access to the state. It can be used outside of a React component. The first argument should be a result of the createStateLink function. For example (see it running):

setTimeout(() => useStateLinkUnmounted(stateRef)
    .set(tasks => tasks.concat([{ name: 'Second task by timeout', priority: 1 }]))
, 5000) // adds new task 5 seconds after website load

The result variable is of type StateLink. The state link variable must be discarded when an event processing is complete. Obtain new state link variable when it is needed in the next event. It is allowed to obtain the state link multiple times within the same event handler.

The result state link inherits all the plugins attached to the state reference.

You can attach more plugins using with method of the state link.

You can also wrap the state link by your custom state access interface using the second transform argument.

useStateLink

This function opens access to the state. It must be used within a functional React component. The first argument should be one of the following:

• global state: a result of the createStateLink function. For example (see it running):

  export const ExampleComponent = () => {
      const state = useStateLink(stateRef);
      return <button onClick={() => state.set(tasks => tasks.concat([{ name: 'Untitled' }]))} >
          Add task
      </button>
  }
  

• local state: initial variable to assign to the local (per component) state. It similar to the original React.createState, but the result StateLink variable has got more features. For example (see it running):

  export const ExampleComponent = () => {
      const state = useStateLink([{ name: 'First Task' }]);
      return <button onClick={() => state.set(tasks => tasks.concat([{ name: 'Untitled' }]))}>
          Add task
      </button>
  }
  

• scoped state: a result of the useStateLink function, called by a parent component either for a global state, for local state or it's parent scoped state. This is discussed in more details below. For example (see it running for global state or for local state):

  const TaskViewer = (props: { taskState: StateLink<Task> }) => {
      const taskState = useStateLink(props.taskState);
      return <p>Task state: {JSON.stringify(taskState.get())}</p>
  }
  

The useStateLink forces a component to rerender everytime when any segment/part of the state is changed AND only if the component used this segment/part of the state.

A segment/part of the state is considered as NOT used by a parent state link, if it is only used by a scoped state link. This gives great rendering peroformance of nested components for large data sets. It is demonstrated in this example for global state, this example for local state and this performance demo.

The global state can be consumed by:

• multiple components as demonstrated in this example
• or by a 'parent' component passing nested links to it's children as demonstarted in this example or this example
• or any combination of the above two options

The result of useStateLink is of type StateLink.

The result state link inherits all the plugins attached to the provided state reference (global state mode) or to the parent component state link (scoped state mode).

You can attach more plugins using with method of the state link.

You can also wrap the state link by your custom state access interface using the second transform argument.

StateLink

The StateLink variable has got the following methods and properties:

• get() (or value is the same) - returns the instance of data in the state

• set(...) or set((prevState) => ...) - function which allows to mutate the state value. If path === [], it is similar to the setState variable returned by React.useState hook. If path !== [], it sets only the segment of the state value, pointed out by the path. The set function will not accept partial updates. It can be done by combining set with nested. There is the Mutate plugin, which adds helpful methods to mutate arrays and objects.

• nested 'converts' a statelink of an object to an object of nested state links OR a statelink of an array to an array of nested state links elements. This allows to 'walk' the tree and access/mutate nested compex data in very convenient way. The result of nested for primitive values is undefined. The typescript support for nested will handle correctly any complexy of the state structure. The result of Object.keys(state.nested) is the same as Object.keys(state.get()). However, nested state links object will have ANY property defined (although not every will pass Typescript compiler check). It is very convenient to create 'editor-like' components for properties, which can be undefined. For example:

  const PriorityEditor = (props: { priorityState: StateLink<number> }) => {
      return <p>Current priority: {priorityState.get() === undefined ? 'unknown' : priority.get()}
          <button onClick={() => priorityState.set(prevPriority =>
              (prevPriority || 0) + 1 // here the value might be not defined, but we can set it!
          )}>
          Increase Priority</button>
      </p>
  }
  const ExampleComponent = () => {
      const taskState: StateLink<Task> = useStateLink({ name: 'Task name is defined but priority is not' });
      return <PriorityEditor priorityState={
          taskState.nested.priority // it will be always defined, but it's value might be not defined
      } />
  }
  

• path 'Javascript' object 'path' to an element relative to the root object in the state. For example:

  const state = useStateLink([{ name: 'First Task' }])
  state.path IS []
  state.nested[0].path IS [0]
  state.nested[0].nested.name.path IS [0, 'name']
  

Transform argument

createStateLink, useStateLinkUnmounted and useStateLink functions accept the second argument, which allows to wrap the state link by custom state access interface. The transform argument is a callback which receives the original state link variable and should return any custom state access instance.

Examples for all possible combinations:

• global state, wrapped state reference:

  const stateInf = createStateLink(initialValue, s => ({
      addTask = (t: Task) => s.set(tasks => tasks.concat([t]))
  }));
  export const useTaskStoreUnmounted = () => useStateLinkUnmounted(stateInf)
  export const useTaskStore = () => useStateLink(stateInf)
  
  useTaskStoreUnmounted().addTask({ name: 'Untitled' })
  
  export const ExampleComponent = () => {
      const state = useTasksStore();
      return <button onClick={() => state.addTask({ name: 'Untitled' })}>
          Add task
      </button>
  }
  

• global state, wrapped state link:

  const stateRef = createStateLink(initialValue);
  const transform = (s: StateLink<Task[]>) => ({
      addTask = (t: Task) => s.set(tasks => tasks.concat([t]))
  })
  
  useStateLinkUnmounted(stateRef, transform).addTask({ name: 'Untitled' })
  
  export const ExampleComponent = () => {
      const state = useStateLink(stateRef, transform);
      return <button onClick={() => state.addTask({ name: 'Untitled' })}>
          Add task
      </button>
  }
  

• local state:

  export const ExampleComponent = () => {
      const state = useStateLink([{ name: 'First Task' }], s => ({
          addTask = (t: Task) => s.set(tasks => tasks.concat([t]))
      }));
      return <button onClick={() => state.addTask({ name: 'Untitled' })}>
          Add task
      </button>
  }
  

• scoped state:

  const TaskViewer = (props: { taskState: StateLink<Task> }) => {
      const taskState = useStateLink(props.taskState, s =>({
          getName = () => s.nested.name.get(),
          setName = (n: string) => s.nested.name.set(n)
      }));
      return <input value={state.getName()} onChange={e => state.setName(e.target.value)} />
  }
  

Transform argument as state value aggregation

You can apply the transform argument to reduce the the state value down to an aggregated value. It works for local, global and scoped states. For example:

const TotalHighestPriorityTasksComponent = (props: { tasksState: StateLink<Task[]> }) => {
    const totalTasksWithZeroPriority = useStateLink(props.tasksState, s => {
        return s.get().filter(t => t.priority === undefined || t.priority === 0).length;
    })
    return <p>Total zero priority tasks: {totalTasksWithZeroPriority}</p>
}

The above will rerender when any task changes a priority or when tasks are added or removed. However, because there is no point to rerender this component when it's aggregated result in the transformation is not changed, we can optimize it:

import { StateLink, Prerender, useStateLink } from '@hookstate/core';

const TotalHighestPriorityTasksComponent = (props: { tasksState: StateLink<Task[]> }) => {
    const totalTasksWithZeroPriority = useStateLink(props.tasksState, s => {
        s.with(Prerender).extended.enablePrerender() // use tripple equals to diff the result
        return s.get().filter(t => t.priority === undefined || t.priority === 0).length;
    })
    return <p>Total zero priority tasks: {totalTasksWithZeroPriority}</p>
}

The above will rerender only when the result of the aggregation is changed. This allows to achieve advanced optimizations for rendering of various aggregated views.

The second argument of the transform callback is defined and equals to the result of the last transform call, when the transform is called by Hookstate to check if the component should rerender. If the core Prerender plugin is enabled and the result of the transform is the same as the last result, Hookstate will skip rerendering the component. This is used by EqualsPrerender plugin, which works with complex data structures the same way as we optimized rerendering of the primitive result number.

Plugins

Please, submit pull request if you would like yours plugin included in the list.

Plugin	Description	Example	Package	Version
Initial	Enables access to an initial value of a StateLink and allows to check if the current value of the StateLink is modified (compares with the initial value). Helps with tracking of modified form field(s).	Demo	@hookstate/initial
Touched	Helps with tracking of touched form field(s).	Demo	@hookstate/touched
Validation	Enables validation and error / warning messages for a state. Usefull for validation of form fields and form states.	Demo	@hookstate/validation
Persistence	Enables persistence of managed states to browser's local storage.	Demo	@hookstate/persistence
Mutate	Adds mutate actions specific for arrays (push, pop, insert, remove, swap, etc..), objects (merge, etc.), strings and numbers.	Demo	@hookstate/mutate
Logger	Logs state updates and current value of a StateLink to the development console.	Demo	@hookstate/logger