javascript-practice

Object methods

• object.method returns Reference Type

  var hi = user.hi;
  hi();
  // hi's "this" is undefined
  

• Arrow functions don't have their own this. Taken from outer function.

Map

• Map allows for keys of any data type -> doesn't convert to string like objects

Prototypal inheritance

SubClass.prototype.__proto__ = BaseClass.prototype;
// or like this:
SubClass.prototype = Object.create(BaseClass.prototype);

Promises

new Promise(
    (resolve, reject) => resolve(1) // (*)
).then(
    result => console.log(result) // (**)
);

• (*) promise executor
• (**) promise handler

When a promise is ready, its .then/catch/finally handlers are put into the queue. They are not executed yet. Javascript engine takes a task from the queue and executes it, when it becomes free from the current code.

• .then/catch/finally is called after the current code is finished.
• Microtask queue has a higher priority than the macrotask queue.
• As a side effect, macrotasks are handled only when promises give the engine a “free time”. -> Macrotasks run after the code is finished and after the microtask queue is empty.

Modules

• Modules are executed only once when there are multiple imports. Good for configuration, where module values are set only on first import, and then used throughout all imports.