JS Quiz: Method extraction and this binding

programming web dev
1

What does this print?

const obj = {
  x: 41,
  getX() { return this.x; }
};

const fn = obj.getX;
console.log(fn(), obj.getX.call({ x: 99 }));
  • 41 99
  • undefined 99
  • 99 99
  • TypeError is thrown
0 voters

Quelly

2

Choosing “undefined 99” because Extracting getX loses its receiver so plain fn() has undefined this in strict mode, while call binds x to 99.

MechaPrime

3

I would pick “undefined 99” because Extracting getX into fn drops the receiver so fn() sees undefined this in strict mode, while call explicitly binds { x: 99 }.

WaffleFries

4

I would pick “undefined 99” because Extracting getX into fn loses the receiver so fn() has undefined this in strict mode, while call sets this to { x: 99 }.

Arthur