Rerender view on browser resize with React

It's a simple and short example of using es6 without jQuery.

import React, { Component } from 'react';

export default class CreateContact extends Component {
  state = {
    windowHeight: undefined,
    windowWidth: undefined
  }

  handleResize = () => this.setState({
    windowHeight: window.innerHeight,
    windowWidth: window.innerWidth
  });

  componentDidMount() {
    this.handleResize();
    window.addEventListener('resize', this.handleResize)
  }

  componentWillUnmount() {
    window.removeEventListener('resize', this.handleResize)
  }

  render() {
    return (
      <span>
        {this.state.windowWidth} x {this.state.windowHeight}
      </span>
    );
  }
}

hooks

import React, { useEffect, useState } from "react";

let App = () => {
  const [windowWidth, setWindowWidth] = useState(0);
  const [windowHeight, setWindowHeight] = useState(0);
  let resizeWindow = () => {
    setWindowWidth(window.innerWidth);
    setWindowHeight(window.innerHeight);
  };

  useEffect(() => {
    resizeWindow();
    window.addEventListener("resize", resizeWindow);
    return () => window.removeEventListener("resize", resizeWindow);
  }, []);

  return (
    <div>
      <span>
        {windowWidth} x {windowHeight}
      </span>
    </div>
  );
};

A very simple solution:

resize = () => this.forceUpdate()

componentDidMount() {
  window.addEventListener('resize', this.resize)
}

componentWillUnmount() {
  window.removeEventListener('resize', this.resize)
}

@SophieAlpert is right, +1, I just want to provide a modified version of her solution, without jQuery, based on this answer.

var WindowDimensions = React.createClass({
    render: function() {
        return <span>{this.state.width} x {this.state.height}</span>;
    },
    updateDimensions: function() {

    var w = window,
        d = document,
        documentElement = d.documentElement,
        body = d.getElementsByTagName('body')[0],
        width = w.innerWidth || documentElement.clientWidth || body.clientWidth,
        height = w.innerHeight|| documentElement.clientHeight|| body.clientHeight;

        this.setState({width: width, height: height});
        // if you are using ES2015 I'm pretty sure you can do this: this.setState({width, height});
    },
    componentWillMount: function() {
        this.updateDimensions();
    },
    componentDidMount: function() {
        window.addEventListener("resize", this.updateDimensions);
    },
    componentWillUnmount: function() {
        window.removeEventListener("resize", this.updateDimensions);
    }
});

Using React Hooks:

You can define a custom Hook that listens to the window resize event, something like this:

import React, { useLayoutEffect, useState } from 'react';

function useWindowSize() {
  const [size, setSize] = useState([0, 0]);
  useLayoutEffect(() => {
    function updateSize() {
      setSize([window.innerWidth, window.innerHeight]);
    }
    window.addEventListener('resize', updateSize);
    updateSize();
    return () => window.removeEventListener('resize', updateSize);
  }, []);
  return size;
}

function ShowWindowDimensions(props) {
  const [width, height] = useWindowSize();
  return <span>Window size: {width} x {height}</span>;
}

The advantage here is the logic is encapsulated, and you can use this Hook anywhere you want to use the window size.

Using React classes:

You can listen in componentDidMount, something like this component which just displays the window dimensions (like <span>Window size: 1024 x 768</span>):

import React from 'react';

class ShowWindowDimensions extends React.Component {
  state = { width: 0, height: 0 };
  render() {
    return <span>Window size: {this.state.width} x {this.state.height}</span>;
  }
  updateDimensions = () => {
    this.setState({ width: window.innerWidth, height: window.innerHeight });
  };
  componentDidMount() {
    window.addEventListener('resize', this.updateDimensions);
  }
  componentWillUnmount() {
    window.removeEventListener('resize', this.updateDimensions);
  }
}