Copy an array
There are different ways to copy an array
//Define a array const cities = ['New-York', 'Paris', 'Pointe-à-Pitre'] //With slice const citiesWithSlice = cities.slice(0) console.log(citiesWithSlice) //['New-York', 'Paris', 'Pointe-à-Pitre'] //With concat const citiesWithConcat = [].concat(cities) console.log(citiesWithConcat) //['New-York', 'Paris', 'Pointe-à-Pitre'] //With spread operator const citiesWithSpread = [...cities] console.log(citiesWithSpread) //['New-York', 'Paris', 'Pointe-à-Pitre'] ⚠ this type of copy it's a shallow copy and not a deep copy see this link
Get object length
//Define an object const user = { lastname: "Doe", firstName: "John", age: 99 } //Transform the object to array and use the length property to it const userLength = Object.keys(user).length console.log(userLength) //3 Ternary expression
Instead of a regular if statement like
let isLogged = true; let message; if (isLogged){ message = "Welcome" } else { message = "Sign in" } console.log(message) //Welcome You can use a simple ternary expression
let isLogged = true; let message = isLogged ? "Welcome" : "Sign in" console.log(message) //Welcome Merge multiple objects
In this case we have different objects but we want now to have only one.
let's see
const defaultUser = { name : "", firstName: "", hasHisLicence: false } const user = { name: "Doe", firstName:"John" } //With Object.assign const data = Object.assign(defaultUser, user); console.log(data) // {name: "Doe",firstName:"John",hasHisLicence: false} //With spread operator const userData = {...defaultUser, ...user} console.log(UserData) // {name: "Doe",firstName:"John",hasHisLicence: false} convert to a boolean
This is a magic trick which convert any type to a boolean it's !! let's see that
const arr = [] console.log(arr.length) //0 console.log(!!arr.length) // false 
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