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Video tutorial: JavaScript Crash Course
Variables
var, let and const
In JavaScript, there’re basically three ways to set variables. We have var, let and const.
var comes into view from the beginning of JavaScript. But you won’t really want to use it anymore now that we’ve got let and const, because var is globally scoped, while let and const has block-level scopes.
With let, you can reassign values. const stands for constant, which means its value cannot be reassigned.
Using const allows you to add values to arrays. You can manipulate it, you can use methods on it. The only thing you can’t do is to take the array and reassign it.
const fruits = ['apples', 'oranges', 'pears']
fruits[3] = 'grapes';
console.log(fruits);
The console prints out grapes as well. This, however, is not the best practice to add a value into an array. See push for a more refined solution.
Only use const unless you know you’re going to reassign the value.