Javascript ES6

Udemy course ES6 Javascript Development from scratch. Get practice with live examples and learn exactly where to apply ES6 features.

Variable declaration

let: ES6 compliant non-constant const: ES6 compliant constant var: pre ES6, still valid

Array Helpers

For Each

Map Helper

Map-Helper

Filter Helper

Filter-Helper

function reject(array, iteratorFunction) {
    console.log(iteratorFunction)
    let permarr = array.filter(iteratorFunction)
    console.log(permarr + " permarr " + Array.isArray(permarr))
    console.log(array + " array " + Array.isArray(array))
    let retarr = array.filter((element) => { return !(permarr.includes(element)) })
    console.log(retarr+ " retar")
  return array.filter((vele) => { return !(permarr.includes(vele)) })
}

Find Helper

Find-Helper

var ladders = [
  { id: 1, height: 20 },
  { id: 3, height: 25 }
];

function findWhere(array, criteria) {
    console.log(Object.keys(criteria) + " criteria keys");
    console.log(Object.values(criteria) + " criteria values");
  return array.find(arr => { 
    console.log(typeof(arr[(Object.keys(criteria))]) + " # " + Number(Object.values(criteria)));
    console.log(arr[(Object.keys(criteria))] === Number(Object.values(criteria)))
    return arr[(Object.keys(criteria))] === Number(Object.values(criteria)) })
}

console.log(findWhere(ladders, { height: 25 })); 

function balancedParens(prev, parStr) {

}

Every and Some Helper

Every returns a boolean for every element evaluated and compared with AND

Every-Helper

Some returns a boolean comparing every element with OR

Some-Helper

Reduce Helper

The reduce helper runs a callback function on each element of an array passing in the previous value as an argument ot the next run. An initial value can be provide see

<!-- parStr.reduce((prev, paStr) => {
    if ( paStr.toArray().filter(char) ={ return char === "\(")} ){
        prev += 1
    } else {
        prev -= 1
    }
    return prev

}, 0) -->

Rest and Spread Helper

The rest takes any arguments given to a function and store them in a array, it is invoked with ...

function rester (...rest) {
    return `DataType ${typeof(rest)} first ${rest[0]} last ${rest.pop()}`
}
rester("a",1,"b",2) //'DataType object first a last 2'

The Spread helper is very similar to the rest helper and returns the flattened array

colors = ["black","red", "gold"];
hex_codes = ["#000000","#FF0000","#FFD700"];
mix = [...colors, ...hexcodes]
Uncaught ReferenceError: hexcodes is not defined
mix = [...colors, ...hex_codes]
// [ 'black', 'red', 'gold', '#000000', '#FF00000', '#FFD700' ]

Destructuring

see MSDN Destructuring limits writing code by intrinsically accessing the desired element

const snubs = [ 'X-Wing', 'TIE-Fighter', 'X-95'];
const [ x ] = snubs;
console.log(x) // X-Wing

Classes

MSDN