react.dev/cookbook/10-props-in-getInitialSate-as-anti-pattern.md

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props-in-getInitialSate-as-anti-pattern	props in getInitialState is an anti-pattern	cookbook	props-in-getInitialSate-as-anti-pattern.html	componentWillReceiveProps-not-triggered-after-mounting.html	dom-event-listeners.html

Problem

You're using this.props in a component getInitialSate, like so:

/** @jsx React.DOM */

var MessageBox = React.createClass({
  getInitialState: function() {
    return {nameWithQualifier: "Mr. " + this.props.name};
  },
  render: function() {
    return <div>{this.state.nameWithQualifier}</div>;
  }
});

React.renderComponent(<MessageBox name="Zuck"/>, mountNode);

Solution

Avoid this (see below for explanation). Compute it directly inside render:

/** @jsx React.DOM */

var MessageBox = React.createClass({
  render: function() {
    return <div>{"Mr. " + this.props.name}</div>;
  }
});

React.renderComponent(<MessageBox name="Zuck"/>, mountNode);

For more complex logic:

/** @jsx React.DOM */

var MessageBox = React.createClass({
  render: function() {
    return <div>{this.getNameWithQualifier(this.props.name)}</div>;
  },
  getNameWithQualifier: function(name) {
    return 'Mr. ' + name;
  }
});

React.renderComponent(<MessageBox name="Zuck"/>, mountNode);

Discussion

This isn't really a React-specific tip, as such anti-patterns often occur in code in general; in this case, React simply points them out more clearly.

Using props, passed down from parent, to generate state often leads to duplication of "source of truth", i.e. where the real data is. Whenever possible, compute values on-the-fly to ensure that they don't get out of sync later on and cause maintenance trouble.