JS class method in a setInterval doesn't work [duplicate]

问题

This question already has answers here:

Javascript setInterval and `this` solution (9 answers)

Closed last year.

I have this simple example with a class with a setInterval that calls main() every 5 seconds. When it comes to call print() it returns me TypeError: this.print is not a function. And I'm really stuck. Why if I call main() without setInterval it works smoothly but with setInterval it fails? It's weird. Any workaround to call main() periodically without this issue?

"use strict";

class test {
  constructor() {
      this.interval = setInterval(this.main, 5000);
  }

  print(){
      console.log('Teeeessssttt');
  }

  main(){
      this.print();
  }
}

const a = new test();

回答1:

You'll need to use bind:

this.interval = setInterval(this.main.bind(this), 5000);

回答2:

You can try setInterval(() => this.main(), 5000) as well. this in JavaScript can differ than what you'd expect the program's source code to suggest. See MDN's take on this.

来源：https://stackoverflow.com/questions/51572081/js-class-method-in-a-setinterval-doesnt-work