Correct prototype chain for Function

Question

What is the correct output (meaning correct by the ECMA standard) of the following program?

function nl(x) { document.write(x + \"
\"); }
nl(Functio         


        

Answer 1

I know this post is kind of old, but I've been searching the net for information on this subject and figured I'd post what I found. The prototype property is for constructor functions. It allows you to assign the prototype object of objects you will create with the new keyword.

Every object in JavaScript has a prototype object, but many implementations don't give you direct access to it or allow you to set it after object creation. In FireFox, you can access this object via the "__proto__" property.

Below I have a version of your code using the "__proto__" property. The section on the Function prototype chain matches what you thought it should have been.

function nl(z) { document.write(z + "
"); }

x = {};

nl(x["__proto__"]);
nl(x["__proto__"] === Object.prototype);

nl("");

nl(nl.prototype.constructor);
nl(nl["__proto__"].constructor);
nl(nl["__proto__"] === nl.prototype);

nl("");

nl(nl["__proto__"]);
nl(nl["__proto__"] === Function.prototype);
nl(nl["__proto__"]["__proto__"] === Object.prototype);
nl(nl["__proto__"]["__proto__"]["__proto__"]);

nl("");

nl(Function["__proto__"]);
nl(Function["__proto__"]["__proto__"]);
nl(Function["__proto__"]["__proto__"] === Object.prototype);
nl(Function["__proto__"]["__proto__"]["__proto__"]);

Output in FireFox is:

[object Object]
true

function nl(z) { document.write(z + "
"); }
function Function() { [native code] }
false

function () { }
true
true
null

function () { }
[object Object]
true
null