Why does new EventEmitter().on("event", array.push) work unexpected

Asked Dec 12 '16 at 20:48

Active Dec 12 '16 at 20:48

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Why does new EventEmitter().on("event", array.push) work unexpected

let array = [];
let a = new EventEmitter();
a.on("event", array.push);       
a.emit("event", 123);
setTimeout(console.log, 1000, array);

Expect: [123]
Actual: []

However, replacing a.on("event", array.push); with a.on("event", (a) => { array.push(a); }); works

asked Dec 12 '16 at 20:48

ATNASGDWNGTH

2

Because the array's `push()` method needs to have `this` point to the array. You can do this instead if you want `a.on("event", array.push.bind(array))`. – idbehold Dec 12 '16 at 21:11
Thanks!! it solves my problem – ATNASGDWNGTH Dec 12 '16 at 21:14

Why does new EventEmitter().on("event", array.push) work unexpected

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