You can find all the code in this post at the repo Github.
OOP related challenges
instanceof
/**
* @param {any} obj
* @param {target} target
* @return {boolean}
*/
// One-line solution
function myInstanceOf(obj, fn) {
return fn.prototype.isPrototypeOf(obj);
}
function myInstanceOf(obj, fn) {
if (typeof obj !== "object" || obj === null) {
return false;
}
if (typeof fn !== "function") {
return false;
}
let proto = Object.getPrototypeOf(obj);
while (proto) {
if (proto === fn.prototype) {
return true;
}
proto = Object.getPrototypeOf(proto);
}
return false;
}
// Usage example
class A {}
class B extends A {}
const b = new B();
console.log(myInstanceOf(b, B)); // => true
console.log(myInstanceOf(b, A)); // => true
console.log(myInstanceOf(b, Object)); // => true
function C() {}
console.log(myInstanceOf(b, C)); // => false
C.prototype = B.prototype;
console.log(myInstanceOf(b, C)); // => true
C.prototype = {};
console.log(myInstanceOf(b, C)); // => false
new
/**
* @param {Function} constructor
* @param {any[]} args
* `myNew(constructor, ...args)` should return the same as `new constructor(...args)`
*/
function myNew(constructor, ...args) {
const obj = {};
Object.setPrototypeOf(obj, constructor.prototype);
const result = constructor.call(obj, ...args);
if (typeof result !== "object" || result == null) {
return obj;
} else {
return result;
}
}
// Usage example
function Person(name) {
this.name = name;
}
const person = myNew(Person, "Mike");
console.log(person); // => Person { name: 'Mike' }
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