What does the new keyword do that allows the following binding on the this object:
function Person(first, last) {
this.first = first;
this.last = last;
}
Person.prototype.greet = function() {
console.log(`Hello, ${this.first} ${this.last}.`);
};
let p = new Person('Tom', 'Jones');
p.greet();Whereas without the new keyword, this.first would raise an error since it is undefined. Conceptually speaking, what is new doing here in how it modifies the function?
Without new:
function Person(first, last) {
this.first = first;
this.last = last;
}
Person('Tom', 'Jones');
// TypeError: Cannot set property 'first' of undefinedAnd without using new seems the following is a crude way to simulate it:
function Person(first, last) {
this.first = first;
this.last = last;
return this;
}
Person.prototype.greet = function() {
console.log(`Hello, ${this.first} ${this.last}.`);
};
Person.prototype.greet.call(Person.call({}, 'Tom', 'Jones'));