luketevl / learn-javascript

Learn about Javascript(es6, es7) and future versions

learn-javascript

Learn about Javascript(es6, es7) and future versions

LINKS

• https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/import
• http://exploringjs.com/es6/ch_modules.html
• https://medium.freecodecamp.com/javascript-modules-a-beginner-s-guide-783f7d7a5fcc#.b592lxm37

Promise

• Resolve all promises

Promise.all([]);

• Return the first promisse in any romises

Promise.race([]);

Symbol

This is new type, are immutable and unique

• Creating symbol

const foo = Symbol('name');
const bar = Symbol('name');
foo == bar // return FALSE

• Get propertySymbols

Object.getOwnPropertySymbol(obj);

Iterators and Iterable

Return {value: any, done: boolean} Element can be iterator

const example = "example";
const it = example[Sysmbol.iterator]();
it.next();

Generators

Run function in steps

• Creating add * in function name
  • Yield is equal return but is possible continue the function after the yield
  • Call the interator use .next()

function* getNames(){
  yield 'Lukete';
  yield 'Henrique';
}
const names = getNames();
names.next();

Proxy

• Creating proxy
  • params: obj, handler

const obj = {
  name: 'Lukete',
  age: 25
}
const proxy = new Proxy(obj, {
  get(target, name){
    console.log('Request name');
  },
  set(target, name, value){
    console.log('Request name');
  }
})

SET

Is iterables

• Use size

let mySet = new Set(['lukete', 'henrique']);
mySet.size;

• Add element ignore equals values

let mySet = new Set(['lukete', 'henrique']);
mySet.add('souza');

• Delete element

let mySet = new Set(['lukete', 'henrique']);
mySet.delete('henrique');

• Verify if exists element

let mySet = new Set(['lukete', 'henrique']);
mySet.has('henrique');

• Get itarables element

let mySet = new Set(['lukete', 'henrique']);
mySet.values();

WeakSet and WeakMap

Only accept object, have equals functions in SET BUT weakset doesnt are iterable

• Creating weakset

let obj1 = {
  name: 'lukete',
  age: 25,
};
let obj2 = {
  name: 'henrique',
  age: 22,
};

let ws = new WeakSet([ob1, obj2]);

MAP

Key and Value, equal SET are iterable

• Creating

let m = new Map();
m.set('lukete', 25);

MODULES

Small, one function. Helpt with manutenabilit. Namespacing local. Reusability

IMPORT

• Structure `import method from library;
• Forms to use import  - * call all methods  - methodName or { methodName } call specific method
  • use without { } IF export is UNIQUE.  - as define alias  - Using alias

import * as Alias from lib;
Alias.method();

import { methodName } from lib;
methodName();

EXPORT

• Any export* pear file
  • import with same name
  • import required use {}

export function name1(){};
export function name2(){};
function name3(){};
function name4(){};
export { name3, name4 }

• Only ONE export default pear file  - import with any name
  • import without use {}

export default name;

Observations

• Style Guide is very important
• Husky
• Only run in changed files
• WeakMap
  • garbacolletion delete automatic
• EXPORT
  • Alias are optional.