Variable name as a string in Javascript

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 = 'John';
alert(variablesName(myFirstName) + ":" + myFirstName);

--> myFirstName:John

UPDATE

I'm trying to connect a browser and another program using JavaScript. I would like to send instance names from a browser to another program for callback method:

FooClass = function(){};
FooClass.someMethod = function(json) {
  // Do something
}

instanceA = new FooClass();
instanceB = new FooClass();
doSomethingInAnotherProcess(instanceB); // result will be substituted by using instanceB.someMethod();

...

From another program:

evaluateJavascriptInBrowser("(instanceName).someMethod("resultA");");

In PHP: https://stackoverflow.com/questions/255312/how-to-get-a-variable-name-as-a-string-in-php/255335#255335

Like Seth's answer, but uses Object.keys() instead:

const varToString = varObj => Object.keys(varObj)[0]

const someVar = 42
const displayName = varToString({ someVar })
console.log(displayName)

You can use the following solution to solve your problem:

const myFirstName = 'John'
Object.keys({myFirstName})[0]

// returns "myFirstName"

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]);

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/

var x = 2;
for(o in window){ 
   if(window[o] === x){
      alert(o);
   }
}

However, I think you should do like "karim79"

Probably pop would be better than indexing with [0], for safety (variable might be null).

const myFirstName = 'John'
const variableName = Object.keys({myFirstName}).pop();
console.log(`Variable ${variableName} with value '${variable}'`);

// returns "Variable myFirstName with value 'John'"

This works for basic expressions

const nameof = exp => exp.toString().match(/[.](\w+)/)[1];

Example

nameof(() => options.displaySize);

Snippet:

var nameof = function (exp) { return exp.toString().match(/[.](\w+)/)[1]; };
var myFirstName = 'Chuck';
var varname = nameof(function () { return window.myFirstName; });
console.log(varname);

Get a string from any valid Javascript (variable, class):

const nameOf = (f) => (f).toString().replace(/[ |\(\)=>]/g,'');

Examples:

nameOf(() => myVariable)             // myVariable
nameOf(() => myVariable.name)        // myVariable.name
nameOf(() => myVariable.name.length) // myVariable.name.length
nameOf(() => myVariable.name[10])    // myVariable.name[10]
nameOf(() => MySuperClass)           // MySuperClass

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.

Shortest way I have found so far to get the variables name as a string:

const name = obj => Object.keys(obj)[0];

const whatsMyName = "Snoop Doggy Dogg";

console.log( "Variable name is: " + name({ whatsMyName }) );
//result: Variable name is: whatsMyName

Since ECMAScript 5.1 you can use Object.keys to get the names of all properties from an object.

Here is an example:

// Get John’s properties (firstName, lastName)
var john = {firstName: 'John', lastName: 'Doe'};
var properties = Object.keys(john);

// Show John’s properties
var message = 'John’s properties are: ' + properties.join(', ');
document.write(message);

best way using Object.keys();

example : for getting multi variables names in global scope

// multi variables for testing
var x = 5 , b = true , m = 6 , v = "str";

// pass all variables you want in object
function getVarsNames(v = {}){
    // getting keys or names !
    let names = Object.keys(v);
    // return array contain all names of variables 
    return names;
}

// testing if that work or not 
let VarsNames = getVarsNames({x , b , m , v});

console.log(VarsNames); // output is array [x , b , m , v]

For those who would like to print variableName and variableValue for debugging purposes, here is a function:

const printNameValue = (v)=> {
  var varName = (v).toString().replace(/[ |\(\)=>]/g, '')
  var varValue = (v)()
  // neat : console.log(varName,varValue);
  // with some coloring  : 
  console.log("\033[1;96m[\033[1;33m " + varName + " :\033[0;0m " + varValue+"\033[1;96m ]\033[0;0m");
}

Example:

const myNiceVariable = 1234
call:
printNameValue(()=> myNiceVariable )
result:

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.

When having a function write a function that changes different global variables values it is not always myfirstname it is whatever happens to be passing through. Try this worked for me.

_{Run in jsfiddle}

var jack = 'jill';
function window_getVarName(what)
{
  for (var name in window)
  {
    if (window[name]==what)
    return(name);
  }
  return("");
}
document.write(window_getVarName(jack));

Will write to the window 'jack'.

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.

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

If you're looking for something quick and dirty, this might work:

var zox = 150;

cl("zox");

function cl(c) {
	console.log(c + ': ' + this[c]); // zox: 150	
}

I've created this function based on JSON as someone suggested, works fine for my debug needs

function debugVar(varNames){
let strX = "";
function replacer(key, value){
    if (value === undefined){return "undef"}
    return value
    }    
for (let arg of arguments){
let lastChar;
    if (typeof arg!== "string"){
        let _arg = JSON.stringify(arg, replacer);
        _arg = _arg.replace('{',"");
        _arg = _arg.replace('}',"");            
        _arg = _arg.replace(/:/g,"=");
        _arg = _arg.replace(/"/g,"");
        strX+=_arg;
    }else{
    strX+=arg;
    lastChar = arg[arg.length-1];
    }
    if (arg!==arguments[arguments.length-1]&&lastChar!==":"){strX+=" "};
}
console.log(strX)    
}
let a = 42, b = 3, c;
debugVar("Begin:",{a,b,c},"end")

No, there is not.
Besides, if you can write variablesName(myFirstName), you already know the variable name ("myFirstName").