Hoisting is a JavaScript mechanism where variables, function declarations and classes are moved to the top of their scope before code execution. Remember that JavaScript only hoists declarations, not initialisation. Let's take a simple example of variable hoisting,
console.log(message); //output : undefined
var message = "The variable Has been hoisted";
The above code looks like as below to the interpreter,
var message;
console.log(message);
message = "The variable Has been hoisted";
In the same fashion, function declarations are hoisted too
message("Good morning"); //Good morning
function message(name) {
console.log(name);
}This hoisting makes functions to be safely used in code before they are declared.
