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javascript: I need to get an object key from the function argument

vm.contributorAmountPerYear[index-1] gets me an object, and I want its key to be the year argument of the function.
function getAgriAmount(year,amount,index) {
if (typeof amount !== "number" ) {
amount = parseInt(amount ||0);
};
var argiYearlyLocalCost = vm.argiterraYearlyLocalCost;
console.log(vm.contributorAmountPerYear[index-1].year);
}

vm.contributorAmountPerYear[index-1][year]

For any javascript object, you should keep in mind that if you use . dot notation, you cannot access the properties for keys that come from a variable and are determined at runtime. Use square bracket notation [] for such a case. This should work:
vm.contributorAmountPerYear[index-1][year];
Dot notation should be used when you already know the key:
var cuteJavaScriptObject = {
animal : 'cat'
}
var myVar = 'animal';
console.log(cuteJavaScriptObject.animal); // OK
console.log(cuteJavaScriptObject.myVar); // Wrong !!
console.log(cuteJavaScriptObject[myVar]); // Now OK

Difference between javascript object literal notation and adding to objects

Can someone explain what is happening in the code below? I'd expect toString to get called for either both foo and bar, or neither. How is literal object notation different from adding fields to an object after it is created?
function Obj(v) {
this.v = v;
};
Obj.prototype.toString= function() {
window.alert("to string called for " +
this.v);
return this.v.toString();
}
var foo = new Obj('foo');
var bar = new Obj('bar');
// toString is not called here.
var map = {foo : 'blah'};
// toString is called here.
map[bar] = "blah2";
Why do object literals not use toString() while adding to an existing object does use toString()?
http://jsfiddle.net/pByGJ/2/

The main reason that object literals don't evaluate the identifier to the left of the colon is so you're not force to quote all literal names (as you do in JSON).
Bracket notation forces you to quote property names, if you don't, it will be evaluated as a variable.
The reason toString() does get called in the second example is because bar has to be converted to a string to be used as a property name.
In your first example, you're just creating a literal object (that is the exactly the same as {"foo" : 'blah'}). So that is never using the variable foo
If you want to create an object using a variable name, you can't use literal object notation, you have to use [] which is what forces it to call toString()
Here's a function to create objects with variable names in one expression.
function obj(key, value /*, key, value, ... */) {
var obj = {};
for (var i = 0, ln = arguments.length ; i < ln; i+=2) {
obj[arguments[i]] = arguments[i+1];
}
return obj;
}
Clearer Example
The fact that your variable names and values are the same doesn't help understanding the problem. Let me suggest this code
var foo = new Obj('fooValue');
var bar = new Obj('barValue');
var map = {foo : 'blah'};
map[bar] = "blah2";
// You expect map to be {fooValue: 'blah', barValue: 'blah2'}
// But it's {foo: 'blah', barValue: 'blah2'}
To do what you need, use my obj function
// Almost as clear as literal notation ???
var map = obj(
foo, 'blah',
bar, 'blah2'
);
// map = {fooValue: 'blah', barValue: 'blah2'} Yay!!

keys in an object literal are taken as strings, not interpreted as variables. This:
var map = {foo : 'blah'};
is equivalent to this:
var map = {"foo" : 'blah'};
and this:
var map = {};
map["foo"] = "blah";
but is completely different than this:
var map = {};
map[foo] = "blah";

LocalStorage, JavaScript and Objects

I need to store an object in localStorage - and I know that in order to do so, I have to convert the object into a string. All cool.
My problem is in actually creating the object in the first place: I have two values in sessionStorage that need to be added to the object which is then passed into localStorage. However, when I try to create the object, one value is being stored as the variable name rather than its (numeric) value. Any idea whats going on here?
var siteName = sessionStorage['1'];
var siteID = (+sessionStorage['2']);
var temp = {siteID:siteName};
alert(typeof siteID);
alert(JSON.stringify(temp));
The first alert confirms that siteID is indeed a number type, but the second alert shows that the variable name (siteID) is stored rather than its numeric value.

This line:
var temp = {siteID:siteName};
...creates an object containing a property called siteId with the value taken from the siteName variable.
If you want the property name to be taken from the siteID variable instead:
var temp = {};
temp[siteID] = siteName;
Or in ES2015 (aka "ES6") you could use the new computed property name syntax:
// ES2015+ only!
var temp = {[siteId]: siteName};
In JavaScript, you can access/create properties on objects in two different but equal ways: Using dotted notation with a literal property name:
obj.foo = "bar"; // Creates a `foo` property on `obj` with the value `"bar"`
...or using bracketed notation and a string:
obj["foo"] = "bar"; // Does the same thing
The keys in object initializers like your var temp = {siteID:siteName}; are always used literally (although they can optionally be in quotes); there's no way with an object initializer to have a key taken from a variable instead. So you have to do it as a two-step process, first create the object, then set the property.
So, if you do
temp[siteID] = siteName;
...the number in siteID will be converted to a string and will become the property name, with the value of siteName being the value.
var temp = {};
var key = 1;
temp[key] = "value";
console.log(temp[1]); // "value"
console.log(temp["1"]); // "value"
(Property names are always strings in JavaScript [for now].)

Change it to this.
var temp = {};
temp[siteName] = siteID;
Or if the typeof test was meant to show the property name, you'd reverse them.
var temp = {};
temp[siteID] = siteName;
But be aware that siteID is considered a String from that point forward.

How can I store reference to a variable within an array?

I'm trying to create an array that maps strings to variables. It seems that the array stores the current value of the variable instead of storing a reference to the variable.
var name = "foo";
var array = [];
array["reference"] = name;
name = "bar";
// Still returns "foo" when I'd like it to return "bar."
array["reference"];
Is there a way to make the array refer to the variable?

Put an object into the array instead:
var name = {};
name.title = "foo";
var array = [];
array["reference"] = name;
name.title = "bar";
// now returns "bar"
array["reference"].title;

You can't.
JavaScript always pass by value. And everything is an object; var stores the pointer, hence it's pass by pointer's value.
If your name = "bar" is supposed to be inside a function, you'll need to pass in the whole array instead. The function will then need to change it using array["reference"] = "bar".
Btw, [] is an array literal. {} is an object literal.
That array["reference"] works because an Array is also an object, but array is meant to be accessed by 0-based index. You probably want to use {} instead.
And foo["bar"] is equivalent to foo.bar. The longer syntax is more useful if the key can be dynamic, e.g., foo[bar], not at all the same with foo.bar (or if you want to use a minimizer like Google's Closure Compiler).

Try pushing an object to the array instead and altering values within it.
var ar = [];
var obj = {value: 10};
ar[ar.length] = obj;
obj.value = 12;
alert(ar[0].value);

My solution to saving a reference is to pass a function instead:
If the variable you want to reference is called myTarget, then use:
myRef = function (newVal) {
if (newVal != undefined) myTarget = newVal;
return myTarget;
}
To read the value, use myRef();. To set the value, use myRef(<the value you want to set>);.
Helpfully, you can also assign this to an array element as well:
var myArray = [myRef];
Then use myArray[0]() to read and myArray[0](<new value>) to write.
Disclaimer: I've only tested this with a numerical target as that is my use case.

My solution to saving a reference is to pass a function instead:
If the variable you want to reference is called 'myTarget', then use:
myRef = function (newVal) {
if (newVal != undefined)
myTarget = newVal;
return myTarget;
}
To read the value, use myRef();. To set the value, use myRef(value_to_set);.
Helpfully, you can also assign this to an array element as well:
var myArray = [myRef];
Then use myArray0 to read and myArray[0](value_to_set) to write.
Disclaimer: I've only tested this with a numerical target as that is my use case.

Determine original name of variable after its passed to a function

I've got a feeling this might not be possible, but I would like to determine the original variable name of a variable which has been passed to a function in javascript. I don't know how to explain it any better than that, so see if this example makes sense.
function getVariableName(unknownVariable){
return unknownVariable.originalName;
}
getVariableName(foo); //returns string "foo";
getVariableName(bar); //returns string "bar";
This is for a jquery plugin i'm working on, and i would like to be able to display the name of the variable which is passed to a "debug" function.

You're right, this is very much impossible in any sane way, since only the value gets passed into the function.

This is now somehow possible thanks to ES6:
function getVariableName(unknownVariableInAHash){
return Object.keys(unknownVariableInAHash)[0]
}
const foo = 42
const bar = 'baz'
console.log(getVariableName({foo})) //returns string "foo"
console.log(getVariableName({bar})) //returns string "bar"
The only (small) catch is that you have to wrap your unknown variable between {}, which is no big deal.

As you want debugging (show name of var and value of var),
I've been looking for it too, and just want to share my finding.
It is not by retrieving the name of the var from the var but the other way around : retrieve the value of the var from the name (as string) of the var.
It is possible to do it without eval, and with very simple code, at the condition you pass your var into the function with quotes around it, and you declare the variable globally :
foo = 'bar';
debug('foo');
function debug(Variable) {
var Value = this[Variable]; // in that occurrence, it is equivalent to
// this['foo'] which is the syntax to call the global variable foo
console.log(Variable + " is " + Value); // print "foo is bar"
}

Well, all the global variables are properties of global object (this or window), aren't they?
So when I wanted to find out the name of my variables, I made following function:
var getName = function(variable) {
for (var prop in window) {
if (variable === window[prop]) {
return prop;
}
}
}
var helloWorld = "Hello World!";
console.log(getName(helloWorld)); // "helloWorld"
Sometimes doesn't work, for example, if 2 strings are created without new operator and have the same value.

Global w/string method
Here is a technique that you can use to keep the name and the value of the variable.
// Set up a global variable called g
var g = {};
// All other variables should be defined as properties of this global object
g.foo = 'hello';
g.bar = 'world';
// Setup function
function doStuff(str) {
if (str in g) {
var name = str;
var value = g[str];
// Do stuff with the variable name and the variable value here
// For this example, simply print to console
console.log(name, value);
} else {
console.error('Oh snap! That variable does not exist!');
}
}
// Call the function
doStuff('foo'); // log: foo hello
doStuff('bar'); // log: bar world
doStuff('fakeVariable'); // error: Oh snap! That variable does not exist!
This is effectively creating a dictionary that maps variable names to their value. This probably won't work for your existing code without refactoring every variable. But using this style, you can achieve a solution for this type of problem.
ES6 object method
In ES6/ES2015, you are able to initialize an object with name and value which can almost achieve what you are trying to do.
function getVariableName(unknownVariable) {
return Object.keys(unknownVariable)[0];
}
var foo = 'hello';
var output = getVariableName({ foo }); // Note the curly brackets
console.log(output);
This works because you created a new object with key foo and value the same as the variable foo, in this case hello. Then our helper method gets the first key as a string.
Credit goes to this tweet.

Converting a set of unique variable into one JSON object for which I wrote this function
function makeJSON(){ //Pass the variable names as string parameters [not by reference]
ret={};
for(i=0; i<arguments.length; i++){
eval("ret."+arguments[i]+"="+arguments[i]);
}
return ret;
}
Example:
a=b=c=3;
console.log(makeJSON('a','b','c'));
Perhaps this is the reason for this query

I think you can use
getVariableName({foo});

Use a 2D reference array with .filter()
Note: I now feel that #Offermo's answer above is the best one to use. Leaving up my answer for reference, though I mostly wouldn't recommend using it.
Here is what I came up with independently, which requires explicit declaration of variable names and only works with unique values. (But will work if those two conditions are met.)
// Initialize some variables
let var1 = "stick"
let var2 = "goo"
let var3 = "hello"
let var4 = "asdf"
// Create a 2D array of variable names
const varNames = [
[var1, "var1"],
[var2, "var2"],
[var3, "var3"]
]
// Return either name of variable or `undefined` if no match
const getName = v => varNames.filter(name => name[0] === v).length
? varNames.filter(name => name[0] === v)[0][1]
: undefined
// Use `getName` with OP's original function
function getVariableName(unknownVariable){
return getName(unknownVariable)
}

This is my take for logging the name of an input and its value at the same time:
function logVariableAndName(unknownVariable) {
const variableName = Object.keys(unknownVariable)[0];
const value = unknownVariable[variableName];
console.log(variableName);
console.log(value);
}
Then you can use it like logVariableAndName({ someVariable })