Neanderthals Programming Machines


    1.1.0 • Public • Published


    Console.log Lifecycle events in a React Component

    Questions? Ask me @wildfiction. Or create an issue.


    npm install react-log-lifecycle


    npm install react-log-lifecycle --save-dev


    In your React component:

    import React from 'react';
    import LogLifecyle from 'react-log-lifecycle';
    // Optional flags:
    const flags = {
      // If logType is set to keys then the props of the object being logged
      // will be written out instead of the whole object. Remove logType or 
      // set it to anything except keys to have the full object logged.
      logType: 'keys',
      // A list of the param "types" to be logged.
      // The example below has all the types.
      names: ['props', 'nextProps', 'nextState', 'prevProps', 'prevState']
    export default class MyReactComponent extends LogLifecyle {
      constructor(props) {
        super(props, flags);
      render() {
        console.log('MyReactComponent render');
        return (
          <div>My Component with React Lifecycle Logging</div>

    Output in Console window

    This output is without the optional flags object enabled above. With the flags enabled this will also output the objects or objects' keys.

    #1.1 constructor(props)
      - Start of cycle #1
      - replaces getInitialState()
      - assign to this.state to set initial state.
    #1.2 componentWillMount()
      - Invoked Once (client and server)
      - Can change state here with this.setState()  (will not trigger addition render)
      - Just before render()
    MyReactComponent render
    #1.3 componentDidMount()
      - Invoked Once (client only)
      - refs to children now available
      - integrate other JS frameworks, timers, ajax etc. here
      - Just after render()
      - End of Cycle #1
    #2.1 componentWillReceiveProps(nextProps)
      - Start of cycle #2
      - invoked when component is receiving new props
      - not called in cycle #1
      - this.props is old props
      - parameter to this function is nextProps
      - can call this.setState() here (will not trigger addition render)
    #2.2 shouldComponentUpdate(nextProps, nextState)
      - invoked when new props/state being received
      - not called on forceUpdate()
      - returning false from here prevents component update and the next 2 parts of the Lifecycle: componentWillUpdate() componentDidUpdate()
      - returns true by default;
    #2.3 componentWillUpdate(nextProps, nextState)
      - cannot use this.setState() (do that in componentWillReceiveProps() above)
      - Just before render()
    MyReactComponent render
    #2.4 componentDidUpdate(prevProps, prevState)
      - Just after render()
    #3.1 componentWillUnmount()
      - invoked immediately before a component is unmounted from DOM
      - do cleanup here. e.g. kill timers and unlisten to events such as flux store updates


    npm i react-log-lifecycle

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