Write Concise Declarative Functions with ES6
Const is another keyword to declare a variable when you do not want to change the value of that variable for the whole program. The difference is just that var is for normal variable declaration whose value can be changed, whereas a variable value declared using const keyword cannot be changed.
A function in JavaScript is similar to a procedure—a set of statements that performs a task or calculates a value, but for a procedure to qualify as a function, it should take some input and return an output where there is some obvious relationship between the input and the output.