PureComponent's shallowEqual

class App extends React.PureComponent {
  state={
    ele: {a:'1'}
  }
  trigger=()=>{
    console.log('click')
    this.setState({ele: {a:'1'}})
  }
  render() {
    console.log('render')
    return (
      <div onClick={this.trigger}>click here to trigger setState</div>
    );
  }
}

A simple demo shows that click event triggers render every time. demo

However, according to source code, React.PureComponent’s shouldComponentUpdate() shallowly compares the objects like following, the click event shouldn’t trigger render.

Performs equality by iterating through keys on an object and returning false when any key has values which are not strictly equal between the arguments. Returns true when the values of all keys are strictly equal.

[gaearon]

If you mean individual properties, afaik they’re compared using Object.is algorithm (which is slightly different from === because it also handles NaN).

[jquense]

Oops, yes your right 😛 not thinking clearly. The second point still holds, it’s not shallow ly equal in your example