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Is there a way to tell whether a function parameter was passed as either a literal or as a variable?

I have a function:
function hello(param){ console.log('param is '+param); }
And two calls. First:
hello(123)
Second:
var a=123; hello(a);
Is there any possible way to tell, from within the hello function, whether param was passed as a var or as a literal value?
NOTICE: I am not trying to solve a problem by this. There are many workarounds of course, I merely wanted to create a nice looking logging function. And also wanted to learn the boundaries of JavaScript. I had this idea, because in JavaScript we have strange and unexpected features, like the ability to obtain function parameter names by calling: function.toString and parsing the text that is returned.

No, primitives like numbers are passed by value in Javascript. The value is copied over for the function, and has no ties to the original.
Edit: How about using an object wrapper to achieve something like this? I'm not sure what you are trying to do exactly.
You could define an array containing objects that you want to keep track of, and check if its in there:
var registry = [] // empty registry
function declareThing(thing){
var arg = { value: thing } // wrap parameter in an object
registry.push(arg) // register object
return arg; //return obj
}
function isRegistered(thingObj){
return (registry.indexOf(thingObj) > -1)
}
var a = declareThing(123);
hello(a);
function hello(param){
console.log(isRegistered(param));
}

Angular in the console: get the scope I created (not the whole scope)

I know if I do
angular.element(document.querySelector('<selector-name>')).scope()
I can get the scope. But that gives me everything ($$childTail, $$childHead, etc).
Is there a method that gives me just the $scope elements (variables and functions) that I created on my controller?

One option that, as far as I can tell, provides almost exactly these properties would be to take the difference of the scope that you retrieved (via angular.element(/*...*/).scope()), and that scope's prototype.
Here's a sample function that does that:
function getAssignedScopeProperties(targetScope){
var targetProto = Object.getPrototypeOf(targetScope);
var assignedProperties = {};
for (var prop in targetScope) {
if (targetScope.hasOwnProperty(prop) && typeof targetProto[prop] === "undefined") {
assignedProperties[prop] = targetScope[prop];
}
}
return assignedProperties;
}
And then using the function:
var targetElement = angular.element(document.querySelector('<selector-name>'));
var targetProps = getAssignedScopeProperties(targetElement.scope());
Unfortunately, in Angular 1.3.15 this seems to leave the $$watchersCount property. This does not happen in versions 1.3.14, nor 1.3.16, so it was likely a bug in AngularJS for version 1.3.15.
That said, keeping a guard against $$watchersCount (or a blacklist with it) to defend against versions of Angular with such bugs doesn't feel proper to me. Another option to ensure that this doesn't happen is to include a check for prop.charAt(0) !== "$" in the inner-if, but assuming the objective is to keep all values that are assigned in the controller, removing any that the controller defined starting with a $ would certainly be wrong (of course, the person who built the controller assigning to properties starting with $ is wrong, too, but that's neither here nor there).

Older question with unaccepted answer here.
The short answer is no, angular does not provide a method for getting only user created properties. Additionally it is a bit difficult to copy or even convert a $scope object to JSON.
The slightly longer answer is you can create a custom JSON.stringify function to parse the $scope object.
var cleanScope = function(scope, includeFunctions) {
// custom JSON.stringify function
// borrowed from: https://stackoverflow.com/questions/24806495/how-to-get-plain-object-from-scope-in-angularjs
function scopeStringify(key, value) {
// ignore any key start with '$',
// and also ignore 'this' key to avoid a circular reference issue.
if (typeof key === 'string' && (key.charAt(0) === '$' || key === 'this')) {
return undefined;
}
// by default, JSON.stringify will ignore keys with a function as a value
// pass true as the second param to get back 'function' instead of ignoring
return includeFunctions && typeof value === 'function' ? 'function' : value;
}
return angular.fromJson(JSON.stringify(scope, scopeStringify));
};
// call like so:
console.log('clean $scope: ', cleanScope($scope));
// or pass true as the second param to include functions
console.log('clean $scope: ', cleanScope($scope, true));

No concept of overloading in JavaScript

Check this fiddle or the code below:
function abc(s) {
console.log('in abc(s)');
}
function abc(s, t) {
console.log('in abc(s,t)');
}
abc('1');
The output of this question is always in abc(s,t)
Can someone please explain me whats going on here and why ?

In Javascript there is no overload concept.
You can however write a function that checks how many arguments have been passed by using the arguments value.
function foo(s, t) {
if (arguments.length == 2) {
...
} else {
...
}
}
all arguments that the function expects in the signature but that are not passed by the caller are received as undefined. You can also write variadic functions by simply accessing the n-th argument passed with arguments[i]. Note however that arguments is not a Javascript array, so not all array methods are available for it.
About being able to redefine the same function multiple times without errors things are a bit complex to explain because the rules are strange.
A simple explanation is you could think of is that function is an executable statement like it is in Python and so the last function definition wins. This would be wrong however because, differently from Python, the following is legal Javascript code:
console.log(square(12));
function square(x) { return x*x; }
i.e. you can call a function in lines that are preceding the definition (in a script: of course typing those two lines in a Javascript console wouldn't work).
A slightly more correct explanation is that the compiler first parses all the function definitions (last wins) and then starts executing the code. This mental model works if you don't put functions inside if because what happens in practice in that case is implementation dependent (and I'm not talking about crazy IE, but even that FF and Chrome will do different things). Just don't do that.
You can even use the form
var square = function(x) { return x*x; }
and in this case it's a simple assignment of a "function expression" to a variable that is executed when the flow passed through it (so it's ok to place different implementations of a function inside different if branches, but you cannot call the function before assigning it an implementation).

First, no method overload support in JavaScript (see #6502 workaround).
Second, to describe what you're experiencing, in JavaScript, the last declared function (with the same name) is invoked because the former has been overwritten, It relates to JavaScript Hoisting.
Try to reorder the functions declarations and see the output result again:
function abc(s, t) {
console.log('in abc(s,t)');
}
function abc(s) {
console.log('in abc(s)');
}
abc('1');

In javascript, there is only one function with any given name and if multiple functions with the same name are declared, the last one declared will be the one that is active.
You can however test the arguments that are passed to your function and implement many of the same types of behaviors that function overloading is designed to handle. In fact, in some cases you can do even more.
In your specific example:
function abc(s, t) {
// test to see if the t argument was passed
if (t !== undefined) {
console.log('was called as abc(s,t)');
} else {
console.log('was called as abc(s)');
}
}
abc('1'); // outputs 'was called as abc(s)'
abc('1', '2'); // outputs 'was called as abc(s,t)'
But, you can also get much, much more creative (and useful).
For example, the jQuery .css() method can be called five different ways.
.css( propertyName )
.css( propertyNames )
.css( propertyName, value )
.css( propertyName, function(index, value) )
.css( properties )
The code inside the .css() method examines the type and number of the arguments to figure out which way it is being called and therefore exactly what operation to carry out.
Let's look at how this could be done to figure out which of the 5 forms of this function are being used:
css: function(prop, value) {
// first figure out if we only have one argument
if (value === undefined) {
if (typeof prop === "string") {
// we have a simple request for a single css property by string name
// of this form: .css( propertyName )
} else if (Array.isArray(prop)) {
// we have a request for an array of properties
// of this form: .css( propertyNames )
} else if (typeof prop === "object") {
// property-value pairs of css to set
// of this form: .css( properties )
}
} else {
if (typeof value === "function") {
// of this form: .css( propertyName, function(index, value) )
} else {
// of this form: .css( propertyName, value )
}
}
}
You can also implement optional arguments. For example, jQuery's .hide() can accept many forms. One of the forms is .hide( [duration ] [, complete ] ) where both the duration and the completion function are optional. You can pass nothing, just a duration or both a duration and completion callback function. That could be implemented like this:
hide: function(duration, fn) {
// default the duration to zero if not present
duration = duration || 0;
// default the completion function to a dummy function if not present
fn = fn || function() {};
// now the code can proceed knowing that there are valid arguments for both
// duration and fn whether they were originally passed or not
}
I find one of the most useful ways of using these variable arguments are to allow code to support a variety of different argument types so that no matter what state your arguments are in, you can just pass them as you have them without having to convert them to some universal type. For example, in this implementation of a set object in javascript, the .add() method can take all of these different forms of arguments:
s.add(key)
s.add(key1, key2, key3)
s.add([key1, key2, key3])
s.add(key1, [key8, key9], key2, [key4, key5])
s.add(otherSet) // any other set object
s.add(arrayLikeObject) // such as an HTMLCollection or nodeList
This both accepts a variable number of arguments and it accepts a number of different types for each argument and it will adapt based on what is passed to it. So, you can initialize a set via a list of keys, an array of keys, from another set, from a pseudo array or any mixture of those types. Internally, the code just iterates through each argument that was passed to the function, checks the type of the argument and acts accordingly.
You can see the code here on GitHub for further info on how this is done.

Hashing JavaScript objects

I have a function that receives a list of JS objects as an argument. I need to store information about those objects in a private variable for future reference. I do not want to stuff a property into the objects themselves, I just want to keep it out of band in a dictionary. I need to be able to lookup metadata for an object in sub-linear time.
For this I need a hash function such that, for any two objects o1 and o2,
hash(o1) !== hash(o2) whenever o1 !== o2.
A perfect example of such a hash function would be the memory address of the object, but I don't think JS exposes that. Is there a way?

Each object reference is different. Why not push the object onto an array? Traversing the array looking for an object reference might still perform better than inspecting each object in a recursive manor to generate a hash key.
function Dictionary() {
var values = [];
function contains(x) {
var i = values.length;
while(i--) {
if (values[i] === x) {
return true;
}
}
return false;
}
function count() {
return values.length;
}
function get(i) {
return (i >= 0 && i < values.length) ? values[i] : null;
}
function set(o) {
if (contains(o)) {
throw new Error("Object already exists in the Dictionary");
}
else {
return values.push(o) - 1;
}
}
function forEach(callback, context) {
for (var i = 0, length = values.length; i < length; i++) {
if (callback.call(context, values[i], i, values) === false) {
break;
}
}
}
return {
get: get,
set: set,
contains: contains,
forEach: forEach,
count: count
};
}
And to use it:
var objects = Dictionary();
var key = objects.set({});
var o = objects.get(key);
objects.contains(key); // returns true
objects.forEach(function(obj, key, values) {
// do stuff
}, this);
objects.count(); // returns 1
objects.set(o); // throws an error

To store metadata about objects, you can use an WeakMap:
WeakMaps are key/value maps in which keys are objects.
Note that this API is still experimental and thus not widely supported yet (see support table). There is a polyfill implementation which makes use of defineProperty to set GUIDs (see details here).

Javascript does not provide direct access to memory (or to the file system for that matter).
You'd probably just want to create your properties/variables within the analysis (hash) function, and then return them to where the function was called from to be stored/persisted for later reference.

Thanks everyone who chipped in to reply. You all have convinced me that what I want to do is currently not possible in JavaScript.
There seem to be two basic compromises that someone with this use case can chose between:
Linear search using ===
=== appears to be the only built-in way to distinguish between two identically-valued objects that have different references. (If you had two objects, o1 and o2, and did a deep comparison and discovered that they were value-identical, you might still want to know if they're reference-identical. Besides === you could do something weird like add a property to o1 and see if showed up in o2).
Add a property to the object.
I didn't like this approach because there's no good reason why I should have to expose this information to the outside world. However, a colleague tipped me off to a feature that I didn't know about: Object.defineProperty. With this, I can alleviate my main concerns: first, that my id would show up, unwanted, during object enumeration, and second, that someone could inadvertently alter my id if there were to be a namespace collision.
So, in case anyone comes here wanting the same thing I wanted, I'm putting it up there for the record that I'm going to add a unique id using Object.defineProperty.

getting the name of a variable through an anonymous function

Is it possible to find the name of an anonymous function?
e.g. trying to find a way to alert either anonyFu or findMe in this code http://jsfiddle.net/L5F5N/1/
function namedFu(){
alert(arguments.callee);
alert(arguments.callee.name);
alert(arguments.callee.caller);
alert(arguments.caller);
alert(arguments.name);
}
var anonyFu = function() {
alert(arguments.callee);
alert(arguments.callee.name);
alert(arguments.callee.caller);
alert(arguments.caller);
alert(arguments.name);
}
var findMe= function(){
namedFu();
anonyFu();
}
findMe();
This is for some internal testing, so it doesn't need to be cross-browser. In fact, I'd be happy even if I had to install a plugin.

You can identify any property of a function from inside it, programmatically, even an unnamed anonymous function, by using arguments.callee. So you can identify the function with this simple trick:
Whenever you're making a function, assign it some property that you can use to identify it later.
For example, always make a property called id:
var fubar = function() {
this.id = "fubar";
//the stuff the function normally does, here
console.log(arguments.callee.id);
}
arguments.callee is the function, itself, so any property of that function can be accessed like id above, even one you assign yourself.
Callee is officially deprecated, but still works in almost all browsers, and there are certain circumstances in which there is still no substitute. You just can't use it in "strict mode".
You can alternatively, of course, name the anonymous function, like:
var fubar = function foobar() {
//the stuff the function normally does, here
console.log(arguments.callee.name);
}
But that's less elegant, obviously, since you can't (in this case) name it fubar in both spots; I had to make the actual name foobar.
If all of your functions have comments describing them, you can even grab that, like this:
var fubar = function() {
/*
fubar is effed up beyond all recognition
this returns some value or other that is described here
*/
//the stuff the function normally does, here
console.log(arguments.callee.toString().substr(0, 128);
}
Note that you can also use argument.callee.caller to access the function that called the current function. This lets you access the name (or properties, like id or the comment in the text) of the function from outside of it.
The reason you would do this is that you want to find out what called the function in question. This is a likely reason for you to be wanting to find this info programmatically, in the first place.
So if one of the fubar() examples above called this following function:
var kludge = function() {
console.log(arguments.callee.caller.id); // return "fubar" with the first version above
console.log(arguments.callee.caller.name); // return "foobar" in the second version above
console.log(arguments.callee.caller.toString().substr(0, 128);
/* that last one would return the first 128 characters in the third example,
which would happen to include the name in the comment.
Obviously, this is to be used only in a desperate case,
as it doesn't give you a concise value you can count on using)
*/
}

Doubt it's possible the way you've got it. For starters, if you added a line
var referenceFu = anonyFu;
which of those names would you expect to be able to log? They're both just references.
However – assuming you have the ability to change the code – this is valid javascript:
var anonyFu = function notActuallyAnonymous() {
console.log(arguments.callee.name);
}
which would log "notActuallyAnonymous". So you could just add names to all the anonymous functions you're interested in checking, without breaking your code.
Not sure that's helpful, but it's all I got.

I will add that if you know in which object that function is then you can add code - to that object or generally to objects prototype - that will get a key name basing on value.
Object.prototype.getKeyByValue = function( value ) {
for( var prop in this ) {
if( this.hasOwnProperty( prop ) ) {
if( this[ prop ] === value )
return prop;
}
}
}
And then you can use
THAT.getKeyByValue(arguments.callee.caller);
Used this approach once for debugging with performance testing involved in project where most of functions are in one object.
Didn't want to name all functions nor double names in code by any other mean, needed to calculate time of each function running - so did this plus pushing times on stack on function start and popping on end.
Why? To add very little code to each function and same for each of them to make measurements and calls list on console. It's temporary ofc.
THAT._TT = [];
THAT._TS = function () {
THAT._TT.push(performance.now());
}
THAT._TE = function () {
var tt = performance.now() - THAT._TT.pop();
var txt = THAT.getKeyByValue(arguments.callee.caller);
console.log('['+tt+'] -> '+txt);
};
THAT.some_function = function (x,y,z) {
THAT._TS();
// ... normal function job
THAT._TE();
}
THAT.some_other_function = function (a,b,c) {
THAT._TS();
// ... normal function job
THAT._TE();
}
Not very useful but maybe it will help someone with similar problem in similar circumstances.

arguments.callee it's deprecated, as MDN states:
You should avoid using arguments.callee() and just give every function
(expression) a name.
In other words:
[1,2,3].forEach(function foo() {
// you can call `foo` here for recursion
})
If what you want is to have a name for an anonymous function assigned to a variable, let's say you're debugging your code and you want to track the name of this function, then you can just name it twice, this is a common pattern:
var foo = function foo() { ... }
Except the evaling case specified in the MDN docs, I can't think of any other case where you'd want to use arguments.callee.

No. By definition, an anonymous function has no name. Yet, if you wanted to ask for function expressions: Yes, you can name them.
And no, it is not possible to get the name of a variable (which references the function) during runtime.