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 = '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: How to get a variable name as a string in PHP?

Answer 1

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)

Answer 2

You can use the following solution to solve your problem:

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

// returns "myFirstName"

Answer 3

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 4

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); console.log(varName);

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/

Answer 5

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 ${variableName} with value '${myFirstName}'`); // returns "Variable myFirstName with value 'John'"

Answer 6

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

Answer 7

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);

Answer 8

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

However, I think you should do like "karim79"

Answer 9

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 10

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

Answer 11

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);

Answer 12

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]

Answer 13

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:

Answer 14

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'.

Answer 15

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 16

您可以反映javascript中的类型并获取属性和方法的名称，但是您需要的是 .NET 中的Lambda Expressions Trees类的东西，我认为由于 javascript 中的动态性质和缺乏静态类型系统，这是不可能的。

Answer 17

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 18

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    
}

Answer 19

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")

Answer 20

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