what is this in javascript

index.tsx
// 1. In a function call
function sayHello() {
  console.log(this);
}
sayHello(); // window object

// 2. In a method call
const person = {
  name: 'John',
  sayName: function() {
    console.log(this);
  }
}
person.sayName(); // person object

// 3. In an object's method that uses a callback function
const car = {
  brand: 'Toyota',
  startEngine: function() {
    console.log(`Starting ${this.brand}'s engine`);
  },
  logName: function(callback) {
    callback();
  }
}
car.logName(car.startEngine); // window object (because startEngine is detached from car object)

// 4. Using call(), apply(), or bind()
const truck = {
  brand: 'Ford'
}
car.startEngine.call(truck); // Ford's engine
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