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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,
javascript
1console.log(message); //output : undefined
2
3var message = "The variable Has been hoisted";The above code looks like as below to the interpreter,
javascript
1var message;
2
3console.log(message);
4
5message = "The variable Has been hoisted";In the same fashion, function declarations are hoisted too
javascript
1message("Good morning"); //Good morning
2
3function message(name) {
4
5console.log(name);
6}This hoisting makes functions to be safely used in code before they are declared.
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