Reactjs CSSTransition Component props in TransitionGroup

Question

I'm currently looking into animate a set of divs. I came across this example and it is exactly what i need. As im still a noobie in react, i dont really understand how the props are being fed throw the <Fade> component, inparticular the Fade params ({ children, ...props }). If someone can shed some light that will be greatly appreciated it..

Here is the snippet of Fade

const Fade = ({ children, ...props }) => (
  <CSSTransition
    {...props}
    timeout={1000}
    classNames="fade"
  >
    {children}
  </CSSTransition>
);

Here is the usage:

<div className='container'>
  <TransitionGroup className='todo-list'>
    {this.state.items.map((item, i) => (
      <Fade key={item}>
        <div>
          {`${item} `}
          <button onClick={() => this.handleRemove(i)}>
            &times;
          </button>
        </div>
      </Fade>
    ))}
  </TransitionGroup>
  <button onClick={() => this.handleAdd()}>Add Item</button>
</div>

Answer 1

The props are fed to Fade using Destructuring Assignment For example

const {children, ...props} = {children: 0, propsA: 1, propsB: 2}
console.log(children); // 0
console.log(props); // {propsA: 1, propsB: 2}

... represents Rest & Spread operators

const Fade = ({ children, ...props }) => (); // This ... is Rest Operator
<CSSTransition {...props}/> // This ... is Spread Operator

Here, props.children is those wrapped by Fade, which is:

<div>
 {`${item} `}
 <button onClick={() => this.handleRemove(i)}>
   &times;
 </button>
</div>

Fade is like to wrap things using CSSTransition and conceal some props.
You can actually rewrite as the follows:

<div className='container'>
  <TransitionGroup className='todo-list'>
    {this.state.items.map((item, i) => (
      <CSSTransition key={item} timeout={1000} classNames="fade">
        <div>
          {`${item} `}
          <button onClick={() => this.handleRemove(i)}>
            &times;
          </button>
        </div>
      </CSSTransition>
    ))}
  </TransitionGroup>
  <button onClick={() => this.handleAdd()}>Add Item</button>
</div>