React doesn't reload component data on route param change or query change

Along with componentDidMount, You also need to implement the componentWillReceiveProps or use getDerivedStateFromProps(from v16.3.0 onwards) in Products page since the same component is re-rendered with updated params and not re-mounted when you change the route params, this is because params are passed as props to the component and on props change, React components re-render and not re-mounted.

EDIT: from v16.3.0 use getDerivedStateFromProps to set/update state based on props(no need to specify it in two different lifecyle methods)

static getDerivedStateFromProps(nextProps, prevState) {
   if (nextProps.match.params.product !== prevState.currentProductId){
      const currentProductId = nextProps.match.params.product
      const result = productlist.products.filter(obj => {

        return obj.id === currentProductId;

      })
     return {

        product: result[0],
        currentId: currentProductId,
        result

      }
  }
  return null;
}

Prior v16.3.0, you would use componentWillReceiveProps

componentWillReceiveProps(nextProps) {
    if (nextProps.match.params.product !== this.props.match.params.product) {
      const currentProductId = nextProps.match.params.product
      const result = productlist.products.filter(obj => {

        return obj.id === currentProductId;

      })
      this.setState({

        product: result[0],
        currentId: currentProductId,
        result

      })
    }
  }

Working codesandbox

As Product component is already loaded it will not reload. You have to handle new product id in the below method of component

componentWillReceiveProps(nextProps) {
if(nextProps.match.params.name.product == oldProductId){
  return;
}else {
 //fetchnewProduct and set state to reload
}

With latest version of react(16.3.0 onwards)

static getDerivedStateFromProps(nextProps, prevState){
   if(nextProps.productID !== prevState.productID){
     return { productID: nextProps.productID};
  } 
  else {
     return null;
  }
}

componentDidUpdate(prevProps, prevState) {
  if(prevProps.productID !== this.state.productID){
     //fetchnewProduct and set state to reload
  }
}

Although all the above-mentioned ways will work, I don't see a point to use getDerivedStateFromProps. Based on React docs, "if you want to re-compute some data only when a prop changes, use a memoization helper instead".

Here, instead, I would suggest simply using componentDidUpdate along with changing the Component to PureComponenet.

With reference to React docs, PureComponenets only rerender if at least one state or prop value changes. Change is determined by doing a shallow comparison of state and prop keys.

  componentDidUpdate = (prevProps) => {
    if(this.props.match.params.id !== prevProps.match.params.id ) {
      // fetch the new product based and set it to the state of the component
   };
  };

Please note that the above only work if you change the Component to PureComponent, and obviously, you need to import it from React.