I understand that in JavaScript only function declarations are hoisted, meaning it should print 30 after executing the function sum.
However, I am confused because it is saying diff is not defined. Shouldn't it have been hoisted as well?
sum(10, 20);
diff(10, 20);
function sum(x, y) {
return x + y;
}
let diff = function(x, y) {
return x - y;
} It appears that only function declarations are hoisted, not function expressions where a nameless function is assigned to a variable. The code snippet below demonstrates this concept:
sum(10, 20);
diff(10, 20);
function sum(x, y) {
return x + y;
}
function diff(x, y) {
return x - y;
} If you want to declare diff the way it was done in the original code snippet, you need to move it to the top of your code structure like this:
let diff = function(x, y) {
return x - y;
}
sum(10, 20);
diff(10, 20);
function sum(x, y) {
return x + y;
}
Absolutely, let and const are indeed hoisted in JavaScript, however, they cannot be accessed before their declarations are evaluated during runtime.
You're trying to call the function before you define it.
Here's how you can make it work:
let subtract = function(x, y) {
return x - y;
}
function add(x, y) {
return x + y;
}
console.log(add(10, 20));
console.log(subtract(10, 20));As the function 'diff' is declared, it will be hoisted. However, at the moment when diff(10, 20); is called, the variable 'diff' will not yet be defined with the function itself. For further understanding, I recommend researching the topic of function declaration versus function expression
One key distinction is that Function Expressions do not get hoisted like Function Declarations
In JavaScript, function expressions are not hoisted, unlike function declarations. This means you cannot use a function expression before it is created:
console.log(notHoisted) // undefined
// even though the variable name is hoisted, the definition isn't so it's undefined
notHoisted(); // TypeError: notHoisted is not a function
var notHoisted = function() {
console.log('bar');
};
If you want the function to be hoisted, you should use a Function Declaration.
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