In javascript, var
is used to create variable. With ES6, let
and const
were introduced. Var
still works but its recommended to use let
and const
. Use const
to create constant value whose value never changes and use let
to create variables whose value is going to change.
Arrow function syntax is a bit shorter than the normal syntax since it omits the function
keyword. When we use this
inside an arrow function it will keep its context and not change it.
const multiply = (number) => number * 2;
...names
in the below example is a collector which collects rest of parameters
var [city, ...names] = ["Pune", "Ashish", "Ansu", "Anju"]
console.log(city); // Pune
console.log(names); // ["Ashish", "Ansu", "Anju]
Spread takes all elements, all properties and distributes them in new array. Spread is use to create new object to prevent reference copying as objects and arrays are reference types. So when we reassign arrays or objects, we are copying the pointer, not the value.
const names = ["Pune", "Ashish", "Ansu", "Anju"]
const updatedNames = [...names, "Patel"]
console.log(updatedNames); // [ 'Pune', 'Ashish', 'Ansu', 'Anju', 'Patel' ]
Destructing allows extracting array elements or object properties and store them in variable.
// Array destructuring
[firstName, lastName] = ["Ashish", "Patel"]
console.log(firstName); // Ashish
console.log(lastName); // Patel
// Object destructuring
const { firstName } = { firstName: "Ashish", lastName: "Patel"}
console.log(firstName) // Ashish
Created 2019-01-23T11:57:03+05:30, updated 2022-01-29T02:34:00+00:00 · History · Edit