Javascript get Object property Name

Question

I passed the following object:

var myVar = { typeA: { option1: "one", option2: "two" } }

I want to be able to pull out the key typeA from the above structure.

This value can change each time so next time it could be typeB.

So I would like to know if there is a way for me to do something like the following pseudo code:

var theTypeIs = myVar.key();

This way when I can pass this object and I can pull out the first value of the object, in this case it is typeA and then based on that I can do different things with option1 and option2.

Answer 1

If you know for sure that there's always going to be exactly one key in the object, then you can use Object.keys:

theTypeIs = Object.keys(myVar)[0];

• user3447415: Yes, it will always be one object, the object is a param to a function being called and I just needed to tell what the 'key' was so I can determine what action to take with the 'vaule' portion.

Answer 2

Like the other answers you can do theTypeIs = Object.keys(myVar)[0]; to get the first key. If you are expecting more keys, you can use

Object.keys(myVar).forEach(function(k) {
 if(k === "typeA") {
 // do stuff
 }
 else if (k === "typeB") {
 // do more stuff
 }
 else {
 // do something
 }
});

• zzzzBov: second one should probably be typeB.

Answer 3

If you want to get the key name of myVar object then you can use Object.keys() for this purpose.

var result = Object.keys(myVar); 
alert(result[0]) // result[0] alerts typeA

• major-mann: This returns ["typeA"] not "typeA"

Answer 4

I was searching to get a result for this either and I ended up with;

const MyObject = {
 SubObject: {
 'eu': [0, "asd", true, undefined],
 'us': [0, "asd", false, null],
 'aus': [0, "asd", false, 0]
 }
};

For those who wanted the result as a string:

Object.keys(MyObject.SubObject).toString()

output: "eu,us,aus"

For those who wanted the result as an array:

Array.from(Object.keys(MyObject))

output: Array ["eu", "us", "aus"]

For those who are looking for a "contains" type method: as numeric result:

console.log(Object.keys(MyObject.SubObject).indexOf("k"));

output: -1

console.log(Object.keys(MyObject.SubObject).indexOf("eu"));

output: 0

console.log(Object.keys(MyObject.SubObject).indexOf("us"));

output: 3

as boolean result:

console.log(Object.keys(MyObject.SubObject).includes("eu"));

output: true

---

In your case;

var myVar = { typeA: { option1: "one", option2: "two" } }
 // Example 1
 console.log(Object.keys(myVar.typeA).toString()); // Result: "option1, option2"
 // Example 2
 console.log(Array.from(Object.keys(myVar.typeA))); // Result: Array ["option1", "option2" ]
 
 // Example 3 as numeric
 console.log((Object.keys(myVar.typeA).indexOf("option1")>=0)?'Exist!':'Does not exist!'); // Result: Exist!
 
 // Example 3 as boolean
 console.log(Object.keys(myVar.typeA).includes("option2")); // Result: True!
 
 // if you would like to know about SubObjects
 for(var key in myVar){
 // do smt with SubObject
 console.log(key); // Result: typeA
 }
 // if you already know your "SubObject"
 for(var key in myVar.typeA){
 // do smt with option1, option2
 console.log(key); // Result: option1 // Result: option2
 }