What exactly defines a function expression?

I would like someone to explain to me if a function expression consists of the function value and the variable it is stored in, or if it only refers to the function value itself. When I see the term "function expression," it typically refers to the entire snippet below:

const funcExp = function(){console.log("Hello World!")};

However, this made me wonder about this syntax:

function(){console.log("Hello World!")}

In my opinion, the function expression is just the function value on its own, essentially making it a pure anonymous function, right? It seems odd to call this an anonymous function:

const funcExp = function(){console.log("Hello World!")};

After all, it already has a name in a way - not directly as part of the function value, but as part of the variable it's assigned to. So, I'm curious to know what really defines a function expression - is it the creation of a variable initialized with a function value, or just the function value itself? If it's the former, then what do we call these types of function values

function(){console.log("Hello World!")}
? Are they also considered function expressions? Thanks for your input.

Answer №1

Whenever I come across the term "function expression," it usually refers to the entire code snippet.

To clarify, technically only the

function(){console.log("Hello World!")}
section of that line is considered a function expression, while the left side is a variable declaration. However, some may use the term "function expression" to describe the whole thing as opposed to a "function declaration." For example, this standalone line represents a function declaration:

function func() {console.log("Hello World!")} 

By the way, if you're curious about the specific names for different syntax elements, I recommend experimenting with . This tool allows you to input JavaScript code and view a tree structure outlining the components.

I might be mistaken, but doesn't it seem odd to label this as an anonymous function?:

Because you promptly assign it to a variable named funcExp, it actually does acquire a name. To illustrate, consider the following:

const funcExp = function(){console.log("Hello World!")};
console.log(funcExp.name)

Personally, I wouldn't classify it as an "anonymous function" since it does end up with a name. If you omit assigning it to a variable, then it truly becomes anonymous, as demonstrated below:

function logName(fn) {
  console.log(fn.name);
}

logName(function(){console.log("Hello World!")})

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