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
Top comments (0)