Explicit Binding

Describing Explicit Binding

• Explicit binding occurs when any of the following are used on a function

  • .call()
  • .apply()
  • .bind()
• This is explicit because we're explicitely passing the this contect to .call(), .apply(), or .bind()

Describing the call Method

• The .call() method is used for passing the this keyword as an argument

• Use cases include:

  • Calling a function on a set of objects
  • Calling a function on multiple objects simultaneously
  • Many more

Describing the apply Method

• The .apply() method works almost the same as .call()

• However, .apply() passes in any array of parameters for any optional arguments following the this keyword

  // call
  myFunc.call(thisContext, param1, param2, ...);

// apply myFunc.apply(thisContext, [param1, param2, ...]);

### Illustrating Explicit Binding
```js
function add(obj) {
    return obj.x + obj.y;
}

class Num {
  constructor(x, y) {
    this.x = x;
    this.y = y;
  }
  minus() {
    return y - x;
  }
}

// One use case
let n = [new Num(10,20), new Num(30,40)];
for (let i of n) {
    console.log(add(i));
}
// 30
// 70

// Another use case
let n = new Num(10,20);
console.log(Num.prototype.add(10,20));  // NaN
console.log(Num.prototype.add.call(n));  // 30

References

• Context for this Keyword