Question

I’m looking at some code from EcmaScript.NET and in particular, I’m looking at the definitions in FunctionNode.cs. They’ve provided a relatively descriptive comment above the definitions, but I’m not sure what would my example below qualify as:

/// <summary>
/// There are three types of functions that can be defined. The first
/// is a function statement. This is a function appearing as a top-level
/// statement (i.e., not nested inside some other statement) in either a
/// script or a function.
///
/// The second is a function expression, which is a function appearing in
/// an expression except for the third type, which is...
///
/// The third type is a function expression where the expression is the
/// top-level expression in an expression statement.
///
/// The three types of functions have different treatment and must be
/// distinquished.
/// </summary>
public const int FUNCTION_STATEMENT = 1;
public const int FUNCTION_EXPRESSION = 2;
public const int FUNCTION_EXPRESSION_STATEMENT = 3;

Here is what I’m roughly seeing:

<script>
(function(){document.write("The name is Bond, ")})(),
(function(){document.write("James Bond.")})()
</script>

Would this qualify as a FUNCTION_STATEMENT, FUNCTION_EXPRESSION, FUNCTION_EXPRESSION_STATEMENT?

Update

I guess my question is about the role of the comma:

// Expression
(function(){ document.write('Expression1<br>'); })();
(function(){ document.write('Expression2<br>'); })();

// Expression
var showAlert=function(){ document.write('Expression3<br>'); };
showAlert();

// Declaration
function doAlert(){ document.write('Declaration<br>'); }
doAlert();

// What about this?
(function(){ document.write('What about'); })(), // <-- Note the comma
(function(){ document.write(' this?<br>'); })();

// And now this? 
var a = ((function(){ return 1; })(), // <-- Again, a comma
(function(){ return 2; })());
document.write("And now this? a = " + a);

What are the last two? Expressions or Expression Statements?

Answer 1

Don’t know about EcmaScript.NET, but from my understanding all those functions are function expressions. They are part of a IIFE-invocation, which again is part of a comma-operator expression – in no way “top-level“.

I’d say that the third type are function statements where they are not allowed syntactically, like

if (false) {
    function doSomething() {…}
}

Check out Kangax’ famous article about named function expressions, where their behaviour across engines is summed up (e.g. Gecko’s function statements).