Assign this or that in JavaScript - ECMAScript 2021

In JavaScript - ECMAScript 2021, the this keyword is used to refer to the current object, whereas the that keyword is not a reserved keyword in JavaScript. However, you can still use other variables or object references to assign a value to that.

Here's an example of how to use this keyword in a method of an object:

const person = {
  name: "John",
  age: 30,
  getDetails: function() {
    console.log(Name: ${this.name}, Age: ${this.age});
  }
};
person.getDetails(); // outputs "Name: John, Age: 30"

In the above example, the getDetails method uses this to refer to the person object, which is the current object.

Here's an example of how to assign a value to that using a variable:

const obj = {
  a: 1,
  b: 2,
  c: function() {
    const that = this;
    console.log(that.a + that.b);
  }
};
obj.c(); // outputs 3

In the above example, the c method assigns the value of this to a variable called that. The c method then uses that to refer to the current object and perform a calculation.

Alternatively, you could also assign that using a reference to the current object:

const obj = {
  a: 1,
  b: 2,
  c: function() {
    const that = obj;
    console.log(that.a + that.b);
  }
};
obj.c(); // outputs 3

In this example, the c method assigns the value of obj to the that variable, which refers to the current object.

Note that assigning a reference to this directly to that may not work as intended, since this may change depending on how the function is called. Therefore, it's recommended to assign a reference to the current object instead.