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Write More Reusable React Components with Composable APIs

4:41 React lesson by

To make more composable React components, you can define common APIs for similar component types.

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To make more composable React components, you can define common APIs for similar component types.


Hi Joe not sure if this is the best forum for this type of question so please point me to the place if it isn't.

What sublime package are you using for your typeahead and other react snippets?

Great video series so far!


In reply to egghead.io

Hey - What would you suggest that if we wanted to reuse "NumInput" but "add" some additional props or whatever, is there a way to "extend" it. Because we might want to use NumInput , but might need something additional so its usage isn't so particular.


There's no clear method in React for extending an existing component, but mixins are a great place to start.

You could also wrap the component you want to inherit from and call it's methods using a ref.

var App = react.createClass({
method: function(){
return this.refs.comp.method();
render: function(){
return <InheritFromThisComponent ref="comp" />

In reply to Dean

In your example, the input is an uncontrolled component because you use defaultvalue, instead of a value, is that correct? Does the code need to be changed if I make it a controlled component instead?


Inhale and exhale, you are teaching man!


I am using React version 0.14.0 on a Mac OSX

When I type this code in, it is functional and I am getting an error of "Uncaught TypeError: React.findDOMNode is not a function"

I understand React.findDOMNode is introduced in the 0.13.0 release of React. Why is this error being thrown? Did it get deprecated in 0.14.0?



In React v0.14 some methods like findDOMNode have been moved to a separate package.

Include https://fb.me/react-dom-0.14.0.js in your application and use ReactDOM.findDOMNode, ReactDOM.render, and ReactDOM. unmountComponentAtNode where applicable.

In reply to Abhishek

When creating React components one key tenet should be that your components should be reusable as well as composable. Now here in our code view we've got the Slider component that we created in the refs video, so hopefully you guys saw that, but basically we've got these Slider components that we can drag around and they update their value.


class Slider extends React.Component {
  render() {
    return (
        <input ref="inp" type="range"
          onChange={this.props.update} />

What I'm going to do is strip these down, or strip this down to just one Slider component. So I'll go ahead and get rid of the rest of these guys.

class App extends React.Component {
    this.state = {
      red: 0
    this.update = this.update.bind(this)
      red: ReactDOM.finDOMNode(this.refs.red.refs.inp).value
    return (
        <Slider ref="red" update={this.update} />

When we save that, we can see it's not such a great component, we don't even necessarily need a component for this guy, but what we're going to do is we're going to rename this to NumInput, we're going to create a more composable, more reusable component, taking advantage of the similar APIs between the number input and the range input. So to get us started I'm going to create some prop types, so we've got NumInput.propTypes, set that to an object and for the sake of brevity I'm just going to paste these in, we'll take a quick look at them.

NumInput.propTypes = {
  min: React.PropTypes.number,
  max: React.PropTypes.number,
  step: React.PropTypes.number,
  val: React.PropTypes.number,
  label: React.PropTypes.string,
  update: React.PropTypes.func.isRequired,
  type: React.PropTypes.oneOf(['number', 'range'])

We've got min set to a number, max set to a number, step and value set to a number. We've got a property of label set to a string, and that's going to allow us to take this label right here out of the control of the user and put it into the control of the component. We've got our update method which is our only required method and that has a type of func, and then finally we've got a type property which is type of oneOf, which takes in an array, and we are willing to accept 'number' or 'range' as a string.

Now we're going to go and set up our NumInput.defaultProps, and again I'm just going to paste these in for the sake of brevity. We've got min and max both set to a default of 0, step set to 1, val set to 0, label set to an empty string, and for a default we're going to use 'range'.

NumInput.defaultProps = {
  min: 0,
  max: 0,
  steop: 1,
  val: 0,
  label: '',
  type: 'range'

Now here in our component, going to paste in some initial settings. So our type, min, max, step, and defaultValue are all set to the props that are passed into our component, our update method does not change, we need to implement our label which we'll drop right here after the input.

    onChange={this.props.update} />

We may want to come back and make an option to have that be before or after the input. So to implement that I'm just going to say let label = this.props.label !== '' and if that's the case, we'll go ahead and output a <label> tag, we won't worry about the for value, and it's inner html will be this.props.label, and just for this demo, we'll go ahead and also output this.props.val otherwise it will just be an empty string. We'll go and save that.


let label = this.props.label !== '' ? 
  <label>{this.props.label} - {this.props.val}</label> : ''

So up here where we're utilizing that, we won't need this label right here, go ahead and break this out a bit so we can see. Set our min = 0, our max = 255, our step = 1, our value = this.state.red and we're going to need to coerce that into a number since the component is expecting a number. We'll set our label to red. So let's go ahead and save that and try it out. We've got our Slider, and we've got our label, and we've got our value.

  update={this.update} />

If we wanted to come over here and update our type to be a type of number input, now we've got our number input and everything seems to be working just fine. If we want to mess around and say this our step of 0.01 we can do that. That will step by .01. If we want to switch that back to the default of range, now you can see it is in fact stepping by that decimal value. So now we have a component that's much more reusable and much more composable.

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