Knowledge about
What happens if a function returns return {}, return null, return 1, return true?
The simple answer is to create a code and experiment with it
Code test
Practice is the mother of wisdom
console.table(
[null.undefined.1.true."".Symbol(), { a: 1},1.2]]
.map((v) = > [
v,
function () {
return v;
},
])
.map(([ret, MyConstructor]) = > [
Object.prototype.toString.call(ret),
ret,
new MyConstructor(),
])
);
Copy the code
Simulation function
function myNew(fn, ... args) {
// Create an empty object
const obj = {};
// Link the __proto__ attribute of this object to the constructor prototype object
obj.__proto__ = fn.prototype;
// Call the constructor as this context and receive the return value
const res = fn.apply(obj, args);
The constructor returns the value if it exists and is a reference data type, otherwise the created object is returned
return typeof res === "object" ? res : obj;
}
const c = myNew(Person, "b");
c.say();
Copy the codeconclusion
- The base type returns an empty object
- Reference type Returns the reference type
The interview guide
- The base type returns an empty object
- Reference type Returns the reference type
review
- Again, one of the special things about Javascript that you should keep in mind.
