React is a javascript module to make it easier to work with asynchronous code, by reducing boilerplate code and improving error and exception handling while allowing variable and task dependencies when defining flow.
The react npm package is a JavaScript library for building user interfaces, particularly for single-page applications. It allows developers to create reusable UI components and manage the state of their applications efficiently.
Component-Based Architecture
React allows developers to encapsulate UI logic and design into components, which can then be composed to build complex user interfaces.
class Welcome extends React.Component {
render() {
return <h1>Hello, {this.props.name}</h1>;
}
}
ReactDOM.render(<Welcome name='Jane' />, document.getElementById('root'));State Management
React provides a way to manage the state within components, enabling dynamic and interactive user interfaces.
class Counter extends React.Component {
constructor(props) {
super(props);
this.state = { count: 0 };
}
increment = () => {
this.setState({ count: this.state.count + 1 });
};
render() {
return (
<div>
<p>{this.state.count}</p>
<button onClick={this.increment}>Increment</button>
</div>
);
}
}Lifecycle Methods
React components come with lifecycle methods that are invoked at specific points in a component's lifecycle, allowing developers to hook into the component's creation, updating, and destruction processes.
class Timer extends React.Component {
componentDidMount() {
this.timerID = setInterval(() => this.tick(), 1000);
}
componentWillUnmount() {
clearInterval(this.timerID);
}
tick() {
this.setState({
date: new Date()
});
}
render() {
return (
<div>
<h2>It is {this.state.date.toLocaleTimeString()}.</h2>
</div>
);
}
}Hooks
Hooks are functions that let developers 'hook into' React state and lifecycle features from function components. They provide a way to use stateful logic without writing a class.
import { useState, useEffect } from 'react';
function Example() {
const [count, setCount] = useState(0);
useEffect(() => {
document.title = `You clicked ${count} times`;
});
return (
<div>
<p>You clicked {count} times</p>
<button onClick={() => setCount(count + 1)}>
Click me
</button>
</div>
);
}Vue.js is a progressive JavaScript framework used for building user interfaces. Unlike React, which is only the view layer, Vue includes a more comprehensive set of tools for building web applications, including a routing solution and state management solution.
Angular is a platform and framework for building single-page client applications using HTML and TypeScript. Angular is more prescriptive than React, providing a standard way to structure an application and including a wide array of features out-of-the-box, such as dependency injection, templating, routing, and more.
Preact is a fast, 3kB alternative to React with the same modern API. It provides the thinnest possible Virtual DOM abstraction on top of the DOM. Preact is a good choice for when performance is critical, and the application needs to be as lightweight as possible.
Svelte is a radical new approach to building user interfaces. Whereas traditional frameworks like React and Vue do the bulk of their work in the browser, Svelte shifts that work into a compile step that happens when you build your app, resulting in significantly smaller and faster applications.
React is a javascript module to make it easier to work with asynchronous code, by reducing boilerplate code and improving error and exception handling while allowing variable and task dependencies when defining flow. This project is applying the concepts of Reactive programming or Dataflow to controlling application flow.
This async flow control module is initially designed to work with Node.js but is planned to be extended to browser and other environments.
React gets its name from similarities with how "chain reactions" work in the physical world. You start the reaction and then it cascades and continues until complete.
Also "Reactive Programming" or "Dataflow" describe defining flow which reacts to the data similar to how a spreadsheet updates cells. These are good examples of how React controls flow based on when data is available
It takes inspiration from several projects including:
The tasks can be mixed, meaning you can use async, sync, object method calls, class method calls, etc in the same flow.
Borrowing heavily from Tim and Elijah's ideas for conductor, this async flow control module provides a way to construct a flow from a collection of rules based on functions or methods (referred to as tasks in this module). It allows dependencies to be defined between the tasks so they can run in parallel as their dependencies are satisfied. React can us both variable dependencies and task dependencies.
As tasks complete, React watches the dependencies and kicks off additional tasks that have all their dependencies met and are ready to execute. This allows the flow to run at maximum speed without needing to arbitrarily block tasks into groups of parallel and serial flow.
To reduce the boilerplate code needed and improve error handling, React automatically provides callback functions for your asynchronous code. These React-provided callback functions perform these steps:
npm install react
OR
Pull from github - http://github.com/jeffbski/react
These live in the examples folder so they are ready to run. Also see test/module-use.test.js for more examples as well as the specific tests for the DSL you want to use.
### Example using default DSL// in your foo module
var react = require('react');
// some normal async and sync functions
function loadUser(uid, cb){ }
function loadFile(filename, cb){ }
function markdown(filedata) { }
function writeOutput(html, user, cb){ }
function loadEmailTemplate(cb) { }
function customizeEmail(user, emailHtml, cb) { }
function deliverEmail(custEmailHtml, cb) { }
// define fn, glue together with react, it will parallelize
// starts with name and in/out params, then the tasks
var loadAndSend = react('loadAndSend', 'uid, filename, cb -> err, user',
loadUser, 'uid, cb -> err, user',
loadFile, 'filename, cb -> err, filemd',
markdown, 'filemd -> html', // no cb, implies sync fn
writeOutput, 'html, user, cb -> err, htmlBytesWritten',
loadEmailTemplate, 'cb -> err, emailmd',
markdown, 'emailmd -> emailHtml', // no cb, implies sync fn
customizeEmail, 'user, emailHtml, cb -> err, custEHtml',
deliverEmail, 'custEHtml, cb -> err, custBytesWritten'
);
exports.loadAndSend = loadAndSend; // is a normal fn created by react
// in a different module far far away, use this as any other node function
var foo = require('foo');
foo.loadAndSend(100, 'bar.md', function (err, user) {
// tasks were parallelized based on their depedencies
}
var react = require('react');
function load(res, cb) { setTimeout(cb, 100, null, res + '-loaded'); }
function prefix(prefstr, str, cb) { setTimeout(cb, 100, null, prefstr + str); }
function postfix(str, poststr, cb) { setTimeout(cb, 100, null, str + poststr); }
function upper(str) { return str.toUpperCase(); }
var fn = react();
var errors = fn.setAndValidateAST({
inParams: ['res', 'prefstr', 'poststr'],
tasks: [
{ f: load, a: ['res'], out: ['lres'] },
{ f: upper, a: ['lres'], out: ['ulres'], type: 'ret' },
{ f: prefix, a: ['prefstr', 'ulres'], out: ['plres'] },
{ f: postfix, a: ['plres', 'poststr'], out: ['plresp'] }
],
outTask: { a: ['plresp'] }
});
console.error('errors:', errors); // []
fn('foo', 'pre-', '-post', function cb(err, lres) {
console.error('err:', err); // null
console.error('lres:', lres); // pre-FOO-LOADED-post
});
The main function returned from require('react') can be used to define the AST used for the processing of the rules or flow.
It takes the following arguments to define a flow function:
var react = require('react');
var fn = react('my-flow-name', 'paramName1, paramName2, cb -> err, outParamName1, outParamName2',
functionRefOrMethodStr, 'paramName1, cb -> err, outParamName2', // async cb task
functionRefOrMethodStr2, 'paramName2, paramName1 -> outParamName1' // sync task
);
->. Use the parameter name cb or callback to specify the Node style callback and err to represent the error parameter as the first output parameter of the callback. Literal values can also be specified directly (true, false, numbers, this, null). Literal strings can simply be quoted using single or double quotes.'obj.method'. These can be asynchronous Node-style callback cb(err, ...) functions or synchronous functions which simply return values directly.cb or callback along with err to specify asynchronous Node style cb(err, ...) task, or omit both to specify a synchronous task.A synchronous task can only have a single return parameter._index (zero based index of the task) added to create unique name. If you specify a name, you will also want to indicate a unique name for within the flow otherwise it will get a suffix as well. Example: { name: 'myTaskName' }{ after: 'foo' } or { after: ['foo', 'bar'] }after option. If you want to guarantee that something only runs after something else completes, then it will need to use an output from that task or specify the dependency with an after.The flow function created by react from the input definition is a normal Node-style function which can be used like any other. These flow functions can be defined in a module and exported, they can be passed into other functions, used as methods on objects (the this context is passed in and available).
The abstract syntax tree or AST provided by React represents the data necessary to define the flow. By abstracting this from the DSL, it allows new skins or interfaces to be developed without need to change the core engine.
The AST is normally created at parse time when the React main function is called (or one of the alternate DSL's is called). This can be done a module load time such that after loading the React defined flow function's AST is generated and ready to process eliminating parsing and validation overhead when it is invoked in the future. This has the added advantage that since validation has also been performed that additional syntax issues or incomplete flow defintion errors can be caught quickly.
After the flow function has been created, you can review the generated AST for a function by accessing the ast.
var react = require('react');
var fn = react('my-flow-name', 'paramName1, paramName2, cb -> err, outParamName1, outParamName2',
functionRefOrMethodStr, 'paramName1, cb -> err, outParamName2', // async cb task
functionRefOrMethodStr2, 'paramName2, paramName1 -> outParamName1' // sync task
);
console.error(fn.ast); // output the generated AST
The AST contains the following pieces:
var ast = {
name: flowName,
inParams: [],
tasks: [],
outTask: {},
locals: {}
};
Additional functionality which is not enabled by default but available by requiring additional modules.
For convenience in debugging or in monitoring flow and performance, React has a built-in plugin for easily logging progress to stderr which is activiated by requiring it and specifying a particular flow function to log or use the main react for global logging of all react modules.
require('react/lib/log-events').logEvents(react); // turn on logging for all react functions
// OR
require('react/lib/log-events').logEvents(myReactFn); // turn on logging for a specific function, repeat for other functions as needed
If you want to automatically resolve promises in React without having to manually call when or then, React provides a plugin which will detect the existence of a then method (indicating a promise) at runtime from any inputs to the flow and will internally create when tasks to resolve them before passing the values to other tasks.
require('react/promise-resolve');
Instead of only logging events to stderr (like LogEvents), this plugin fires events that can be directly monitored. The LogEvent plugin uses this internally to get access to the metrics.
It also provides a simple accumulator which can be used to accumulate events. Note that this accumulator is designed for short term debug use, as it will continue to accumulate events and does not have any size restrictions.
Thus while the tracking can be used in production because it simply fires events, the accumulator should only be used for convenience in debugging and testing.
require('react/lib/track-tasks'); // enable tracking and events
// if you want to use the accumulator
var EventCollector = require('react/lib/track-tasks').EventCollector;
var collector = new EventCollector();
collector.captureGlobal('*'); // capture all react events for all flows
// OR
collector.capture(flowFn, 'task.'); // capture task events on a flow
collector.capture(flowFn, 'flow.'); // add capture flow events on a flow
var events = collector.list(); // retrieve the list of events
Additional DSL's can be loaded by requiring them. See the Alternate DSL page for more info.
ok ast.test.js .................... 10/10
ok cb-task.test.js ................ 31/31
ok core-deferred.test.js .......... 11/11
ok core-promised.test.js .......... 11/11
ok core-when.test.js ................ 6/6
ok core.test.js ................. 104/104
ok chain.test.js .................. 74/74
ok fstr.test.js ................... 67/67
ok pcode.test.js .................. 94/94
ok dsl.test.js .................... 70/70
ok event-manager.test.js .......... 13/13
ok exec-options.test.js ............. 3/3
ok finalcb-task.test.js ............. 5/5
ok input-parser.test.js ........... 15/15
ok module-use.test.js ............. 21/21
ok promise-auto-resolve.test.js ..... 4/4
ok ret-task.test.js ............... 31/31
ok task.test.js ..................... 1/1
ok validate-cb-task.test.js ......... 6/6
ok validate-ret-task.test.js ........ 7/7
ok validate.test.js ............... 31/31
ok vcon.test.js ................... 55/55
total ........................... 692/692
ok
Source code repository: http://github.com/jeffbski/react
Ideas and pull requests are encouraged - http://github.com/jeffbski/react/issues
You may contact me at @jeffbski or through github at http://github.com/jeffbski
FAQs
React is a JavaScript library for building user interfaces.
The npm package react receives a total of 12,074,552 weekly downloads. As such, react popularity was classified as popular.
We found that react demonstrated a healthy version release cadence and project activity because the last version was released less than a year ago. It has 4 open source maintainers collaborating on the project.
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