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JavaScript

Question on the event listener on app.js

Hello,

With the event listerner which Listens for click on #begin-game and calls startGame() on game object. When I use arrow function for the event listener, I get a TypeError that 'this' is undefined

const game = new Game();

/** 
 * Listens for click on `#begin-game` and calls startGame() on game object
 */
document.getElementById('begin-game').addEventListener('click', () => {
    game.startGame();
    this.style.display = 'none';
    document.getElementById('play-area').style.opacity = '1';
});

BUT when I use the function keyword it works. Please is there any explanation behind this?

const game = new Game();

/** 
 * Listens for click on `#begin-game` and calls startGame() on game object
 */
document.getElementById('begin-game').addEventListener('click', function(){
    game.startGame();
    this.style.display = 'none';
    document.getElementById('play-area').style.opacity = '1';
});

2 Answers

Here is an explanation on how arrow function binds to "this" https://codeburst.io/javascript-arrow-functions-for-beginners-926947fc0cdc Change "this" to the object itself "document.getElementById('begin-game')" it will work.

Thanks very much