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function declaration vs function expression in javascript Dmitri Pavlutin

AhmedHassan answered on July 30, 2022 Popularity 7/10 Helpfulness 2/10

answer function declaration vs function expression in javascript Dmitri Pavlutin

function declaration vs function expression in javascript Dmitri Pavlutin

Comment

// Function declaration:
function sumA(a, b) {
  return a + b;
}
// Function expression:
(function sumB(a, b) {
  return a + b;
});
sumA(1, 2); // ???
sumB(1, 2); // ???

//As expected, sumA(1, 2) simply returns the sum of 1 and 2 numbers — 3. However, invoking sumB(1, 2) throws an error Uncaught ReferenceError: sumB is not defined.
/*
The explanation is that sumA was created using a function declaration, which creates a function variable (with the same name as the function name) in the current scope. But sumB was created using a function expression (it is wrapped into parentheses), which doesn't create a function variable in the current scope.

If you want to access the function created using a function expression, then save the function object into a variable:
*/
// Works!
const sum = (function sumB(a, b) {
  return a + b;
});
sum(1, 2); // => 3

// continue reading: https://dmitripavlutin.com/javascript-function-expressions-and-declarations/#1-function-expressions-vs-function-declarations

Popularity 7/10 Helpfulness 2/10 Language javascript

Source: dmitripavlutin.com

Tags: function-declaration javascript

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