Arrow Functions Classes Enhanced Object Literals String interpolation Destructuring Default Spread Spread + Object Literals Rest Let Const For..of Unicode Modules & Module Loaders Set WeakSet Map WeakMap Proxies Symbols Inheritable Built-ins New Library Binary and Octal Promises Reflect Tail Call Optimization
Map
Maps are a store for key / value pairs. Key and value could be a primitives or object references.Let’s create a map:let map = new Map(), val2 = 'val2', val3 = { key: 'value' };map.set(0, 'val1'); map.set('1', val2); map.set({ key: 2 }, val3);console.log(map); // Map {0 => 'val1', '1' => 'val2', Object {key: 2} => Object {key: 'value'}}
Set
It’s a collection for unique values. The values could be also a primitives or object references.let set = new Set();set.add(1); set.add('1'); set.add({ key: 'value' });console.log(set); // Set {1, '1', Object {key: 'value'}}
testWeakMap
WeakMaps provides leak-free object keyed side tables. It’s a Map that doesn’t prevent its keys from being garbage-collected. We don’t have to worry about memory leaks.If the object is destroyed, the garbage collector removes an entry from the WeakMap and frees memory.Keys must be objects.It has almost the same API like a Map, but we can’t iterate over the WeakMap collection. We can’t even determine the length of the collection because we don’t have size attribute here.The API looks like this:new WeakMap([iterable])WeakMap.prototype.get(key) : any WeakMap.prototype.set(key, value) : this WeakMap.prototype.has(key) : boolean WeakMap.prototype.delete(key) : boolean
WeakSet
Like a WeakMap, WeakSet is a Seat that doesn’t prevent its values from being garbage-collected. It has simpler API than WeakMap, because has only three methods:new WeakSet([iterable])WeakSet.prototype.add(value) : any WeakSet.prototype.has(value) : boolean WeakSet.prototype.delete(value) : boolean
Generators
Functions in JavaScript, as we all know, “run until return/end”. Generator Functions on the other hand, “run until yield/return/end”. Unlike the normal functions Generator Functions once called, returns the Generator Object, which holds the entire Generator Iterable that can be iterated using next() method or for…of loop.
Every next() call on the generator executes every line of code until the next yield it encounters and suspends its execution temporarily.
1. Default Parameters in ES6
var calculateArea = function(height = 50, width = 80) {
// write logic
...
}
// write logic
...
}
2. Template Literals in ES6
var name = `Your name is ${firstName} ${lastName}.`
3. Multi-line Strings in ES6
let poemData = `Johny Johny Yes Papa,
Eating sugar? No, papa!
Telling lies? No, papa!
Open your mouth Ah, ah, ah!`
Eating sugar? No, papa!
Telling lies? No, papa!
Open your mouth Ah, ah, ah!`
4. Destructuring Assignment in ES6
var o = {p: 42, q: true};
var {p, q} = o;
console.log(p); // 42
console.log(q); // true
var {p, q} = o;
console.log(p); // 42
console.log(q); // true
6. Arrow Functions in ES6
The fat arrows are amazing because they would make your
this behave properly, i.e., this will have the same value as in the context of the function— it won’t mutate.
$('.btn').click((event) => {
this.doSomething()
});
this.doSomething()
});
7. Promises in ES6
var asyncCall = new Promise((resolve, reject) => {
// do something async
resolve();
}).then(()=> {
console.log('Yay!');
})
// do something async
resolve();
}).then(()=> {
console.log('Yay!');
})
8. Block-Scoped Constructs Let and Const
function calculateAmount(boolVal) { let amount = 0; if(boolVal) { let amount = 1; // scope of this amount ends with next closing bracket } return amount; } console.log(calculateAmount(true)); // output: 09. Classes in ES6
class Profile { constructor(firstName, lastName = '') { // class constructor this.firstName = firstName; this.lastName = lastName; } getName() { // class method console.log(`Name: ${this.firstName} ${this.lastName}`); } }let profileObj = new Profile('Kavisha', 'Talsania'); profileObj.getName(); // output: Name: Kavisha Talsania
10. Modules in ES6
In ES6, there are modules with
import and export operands.
export var userID = 10;
export function getName(name) {
...
};
export function getName(name) {
...
};
