Variable name as a string in Javascript

Question

Is there a way to get a variable name as a string in Javascript? (like NSStringFromSelector in Cocoa)

I would like to do like this:

var myFirstName =         


        

Answer 1

Typically, you would use a hash table for a situation where you want to map a name to some value, and be able to retrieve both.

var obj = { myFirstName: 'John' };
obj.foo = 'Another name';
for(key in obj)
    console.log(key + ': ' + obj[key]);

Answer 2

I needed this, don't want to use objects, and came up with the following solution, turning the question around.

Instead of converting the variable name into a string, I convert a string into a variable.

This only works if the variable name is known of course.

Take this:

var height = 120;
testAlert(height);

This should display:

height: 120

This can be done like this:

function testAlert(ta)
{
    a = window[ta];
    alert(ta + ': ' + a); 
}

var height = 120;
testAlert("height");
// displays: height: 120

So I use the string "height" and turn that into a variable height using the window[] command.

Answer 3

var somefancyvariable = "fancy";
Object.keys({somefancyvariable})[0];

This isn't able to be made into a function as it returns the name of the function's variable.

// THIS DOESN'T WORK
function getVarName(v) {
    return Object.keys({v})[0];
}
// Returns "v"

Edit: Thanks to @Madeo for pointing out how to make this into a function.

function debugVar(varObj) {
    var varName = Object.keys(varObj)[0];
    console.log("Var \"" + varName + "\" has a value of \"" + varObj[varName] + "\"");
}

You will need call the function with a single element array containing the variable. debugVar({somefancyvariable});
Edit: Object.keys can be referenced as just keys in every browser I tested it in but according to the comments it doesn't work everywhere.

Answer 4

You can reflect on types in javascript and get the name of properties and methods but what you need is sth like Lambda Expressions Trees in .NET, I think it's not be possible due to dynamic nature and lack of static type system in javascript.

Answer 5

This worked using Internet Explorer (9, 10 and 11), Google Chrome 5:

   
var myFirstName = "Danilo";
var varName = Object.keys({myFirstName:0})[0];
console.log(varName);

Browser compatibility table:
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/keys

Answer 6

In ES6, you could write something like:

let myVar = 'something';
let nameObject = {myVar};
let getVarNameFromObject = (nameObject) => {
  for(let varName in nameObject) {
    return varName;
  }
}
let varName = getVarNameFromObject(nameObject);

Not really the best looking thing, but it gets the job done.

This leverages ES6's object destructuring.

More info here: https://hacks.mozilla.org/2015/05/es6-in-depth-destructuring/