Unlike var, const/let are bound to lexical scope rather than function scope.
{
var x = 1 // will escape the scope
let y = 2 // bound to lexical scope
const z = 3 // bound to lexical scope, constant
}
console.log(x) // 1
console.log(y) // ReferenceError: y is not defined
console.log(z...
Arrow functions automatically bind to the 'this' lexical scope of the surrounding code.
performSomething(result => {
this.someVariable = result
})
vs
performSomething(function(result) {
this.someVariable = result
}.bind(this))
Let's consider this example, that outputs the squares of the numbers 3, 5, and 7:
let nums = [3, 5, 7]
let squares = nums.map(function (n) {
return n * n
})
console.log(squares)
Run in RunKit
The function passed to .map can also be written as arrow function by removing the function keywor...
/* @flow */
function product(a: number, b: number){
return a * b;
}
const b = 3;
let c = [1,2,3,,{}];
let d = 3;
import request from 'request';
request('http://dev.markitondemand.com/MODApis/Api/v2/Quote/json?symbol=AAPL', (err, res, payload)=>{
payload = JSON.parse(payload);...
