Javascript get key name

7 Ways to Get Object Key Name in JavaScript: A Comprehensive Guide

Learn 7 different ways to get the key name of an object in JavaScript with this comprehensive guide. From Object.keys() to Object.entries(), master the art of working with JavaScript objects.

• Using Object.keys() method
• Using Object.getOwnPropertyNames() method
• Using Object.keys() and indexing
• Using Object.getOwnPropertyNames() and indexing
• Using the in operator
• Using the find() method
• Using Object.keys() and filtering
• Using Object.entries() method
• Other helpful examples for getting object key names in JavaScript
• Conclusion
• How to get object key name in JavaScript?
• How to get object variable name in JavaScript?
• How do I get just the keys of an object?
• How to return object property name in JavaScript?

JavaScript is one of the most widely used programming languages in the world, and for good reason. It offers a range of features and capabilities that make it a versatile and powerful tool for web development. One of the most important data structures in JavaScript is the object, which is used to store complex data. When working with objects, it is often necessary to retrieve the key or property name of an object. In this comprehensive guide, we will explore seven different approaches to getting the key name of an object in JavaScript.

Using Object.keys() method

The Object.keys() method is one of the most commonly used methods for retrieving the keys of an object in JavaScript. This method returns an iterator object with the keys of the object. Here is the syntax for using the Object.keys() method:

Here is an example of how to use the Object.keys() method to get the keys of an object:

const obj = < name: "John", age: 30 >; const keysArray = Object.keys(obj); console.log(keysArray); // Output: ["name", "age"] 

Using Object.getOwnPropertyNames() method

Another method for retrieving the keys of an object is the Object.getOwnPropertyNames() method. This method can be used to get all properties, including non-enumerable properties except for those which use Symbol, found in an object. Here is the syntax for using the Object.getOwnPropertyNames() method:

Object.getOwnPropertyNames(obj) 

Here is an example of how to use the Object.getOwnPropertyNames() method to get the properties of an object:

const obj = < name: "John", age: 30 >; const propertiesArray = Object.getOwnPropertyNames(obj); console.log(propertiesArray); // Output: ["name", "age"] 

Using Object.keys() and indexing

To get the key name of an object in JavaScript, one approach is to use Object.keys(objectName)[0] to get the key of the first element of the object. Here is an example:

const obj = < name: "John", age: 30 >; const firstKey = Object.keys(obj)[0]; console.log(firstKey); // Output: "name" 

Using Object.getOwnPropertyNames() and indexing

Another approach is to use Object.getOwnPropertyNames(obj) to return an array of all properties found in the object and then access the key name through indexing. Here is an example:

const obj = < name: "John", age: 30 >; const propertiesArray = Object.getOwnPropertyNames(obj); const firstKey = propertiesArray[0]; console.log(firstKey); // Output: "name" 

Using the in operator

The in operator can be used to check if a specified property/key exists in an object. Here is the syntax for using the in operator:

Here is an example of how to use the in operator to check if a property exists in an object:

const obj = < name: "John", age: 30 >; console.log("name" in obj); // Output: true 

Using the find() method

The find() method can be used to find the key that corresponds to the value in an object. Here is an example:

const obj = < name: "John", age: 30 >; const key = Object.keys(obj).find(key => objJavascript get key name === 30); console.log(key); // Output: "age" 

Using Object.keys() and filtering

The Object.keys() method can be used to get an array of the object’s keys and then filter the key that corresponds to a specific value. Here is an example:

const obj = < name: "John", age: 30 >; const key = Object.keys(obj).filter(key => objJavascript get key name === 30)[0]; console.log(key); // Output: "age" 

Using Object.entries() method

The Object.entries(obj) method can be used to get an array of key/value pairs from an object. Here is an example:

const obj = < name: "John", age: 30 >; const entriesArray = Object.entries(obj); console.log(entriesArray); // Output: [["name", "John"], ["age", 30]] 

Other helpful examples for getting object key names in JavaScript

In Javascript , get object key name in js code sample

var buttons = < foo: 'bar', fiz: 'buz' >;for ( var property in buttons ) < console.log( property ); // Outputs: foo, fiz or fiz, foo >

Conclusion

In conclusion, there are several ways to get the key name of an object in JavaScript. These include using the Object.keys() method, Object.getOwnPropertyNames() method, in operator, find() method, and Object.entries() method. By understanding these methods, you can more easily work with objects in JavaScript and access their properties. It is important to keep in mind that the key names in a JavaScript object must be a string, symbol, or number and that there are best practices for naming keys in an object. With these tools at your disposal, you can write more efficient and effective code in JavaScript.

Frequently Asked Questions — FAQs

How do I get the key name of an object in JavaScript?

To get the key name of an object in JavaScript, you can use various methods such as Object.keys(), Object.getOwnPropertyNames(), in operator, find() method, and Object.entries().

What is the difference between Object.keys() and Object.getOwnPropertyNames()?

Object.keys() method returns only the enumerable properties of an object while Object.getOwnPropertyNames() method returns all properties including non-enumerable properties.

How do I get the first key name of an object in JavaScript?

Can I use the in operator to check if a property/key exists in an object?

How do I find the key name that corresponds to a value in an object?

What are the best practices for naming keys in an object?

In JavaScript, key names in an object must be a string, symbol, or number. It is recommended to use descriptive and meaningful key names that are easy to understand and maintain.

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Get Key of a JavaScript Object

1. Get Key of a Javascript Object With the Object.keys() Method
2. Get Keys of a Javascript Object With the Object.entries(obj) Method
3. Get key of a Javascript Object Using for Loop

A javascript object is a collection of key-value pairs. We need a key to get its value from a javascript object. Key-value pairs are used widely in client-server communications and JavaScript programming. We are aware of retrieving a value from a JSON object provided we have its key. But what if we do not have the key name? How do we get its value from the Javsscript object? Let us look at a few ways in which we can get the keys from a javascript object.

Get Key of a Javascript Object With the Object.keys() Method

The Object.keys() function returns an array containing the keys of the javascript object. We pass the javascript object as a parameter to the Object.keys() function. The output array contains the keys in the same order in which they are in the original javascript object. If we pass an array to the Object.keys() , it will return the array indices as output. And the parameter object is with indices, then the Object.keys() will return an array of those indices. Refer to the following code to understand the usage and behavior of the Object.keys() function.

var fruitsArr1 = ["Apple", "Orange", "Mango", "Banana"]; var fruitsObj2 = < 0: "Apple", 4: "Orange", 2: "Mango", 3: "Banana">; var fruitsObj3 = < "id": "1", "name": "mango", "color": "yellow">; console.log(Object.keys(fruitsArr1)); console.log(Object.keys(fruitsObj2)); console.log(Object.keys(fruitsObj3)); 

["0", "1", "2", "3"] ["0", "2", "3", "4"] ["id", "name", "color"] 

If the keys are numbers, the Object.keys() function will return an array of the numeric keys in sorted order. The fruitsObj2 has the keys numbered 0 , 4 , 2 , 3 . But when we apply the Object.Keys() function, it returns the keys as [«0», «2», «3», «4»] which is in a sorted order. The key-value will still hold the same value mapping as is it did for the original javascript object. For instance, the fruitsObj2 holds 4: «Orange» and at 2: «Mango» , but Object.keys(fruitsObj2) returned their order as «2», «4» . If we were console.log their values at the keys 2 and 4 , we get the correct values as output. Hence, the function has not modified anything in the actual key-value mapping, even if the Object.keys returns the numeric keys of an array or an object in sorted order. Refer to the following code.

console.log(fruitsObj2[2]); console.log(fruitsObj2[4]); 

Get Keys of a Javascript Object With the Object.entries(obj) Method

Object.entries(obj) method is diverse and is more flexible than the Object.keys() function. It splits the entire object into small arrays. Each array consists of key-value pairs in the form Javascript get key name . Using Object.keys() , we get only the keys of an object, but using the Object.entries(obj) , we can get all the entries in an object, including the keys and their values . Object.entries(obj) is not a commonly used method. In most scenarios, we will require to get the keys from an object. The corresponding values can be obtained easily with the help of keys .

Syntax

Parameters

Same as that of the Object.keys() method, the Object.entries(obj) accepts the javascript object as the parameter.

Return

Object.entries(obj) returns the key-value pairs destructed into arrays. The return type will be an array of arrays, each sub-array holding two elements: the key and the value. Something like [Javascript get key name, Javascript get key name, Javascript get key name . ] . The function preserves the order of the object attributes. In the implementation behind the scenes, the key-value pairs are formed by iterating over the object properties. Refer to the following code to better understand the behavior of the Object.entries() function. We use JSON.stringify() to get a human-readable string version of the values output by the function.

var fruitsObj3 = < "id": "1", "name": "mango", "color": "yellow">; console.log(JSON.stringify(Object.entries(fruitsObj3))); 

We can use the Object.entries() in another way. We can iterate over the javascript object and log the attribute keys and their values. The approach is as depicted by the following code snippet.

for (const Javascript get key name of Object.entries(fruitsObj3))   console.log(`$key>: $value>`); > 

id: 1 name: mango color: yellow 

If we are interested in getting the key alone from the Object.entries() function, we can log the key and discard the value part.

Get key of a Javascript Object Using for Loop

Can we use a simple for loop to get the keys from an object? It is not a commonly known feature of a for loop. We can iterate through any javascript object as we do for arrays using the for-in combination. It iterates through each parameter with the i (the iterator) holding the key of the object and the object[i] holding the value corresponding to the key in the object. Let us look at the following code to understand the concept better.

var obj = < "id": "1", "name": "mango", "color": "green">; for(let i in obj)   console.log(i); // key  console.log(obj[i]); // value against the key  > 

id 1 name mango color green 

If we wish to extract only the keys from the object, we can use the iterator value. We can use the console.log(i) in the above code in the for(let i in obj) block.

If we have nested structures in the javascript object, for(let i in obj) can be used to get the key. But, the value for the nested structure will be the structure itself. Refer to the following code.

var a = < "id": "1", "name": "mango", "color": "name": "yellow", "appearance": "bright">>; for(let i in a)  console.log(i);  console.log(a[i]); > 

Related Article — JavaScript Object

Источник

How to Get the First Key Name of a JavaScript Object

In this tutorial, we will discuss the two mathods of getting the first key of a JavaScript Object.

Object.keys

Since objects do not have index referencing, you can’t complete your task by just calling for the first element or last element.

For that purpose, you should use the object.keys method to get access to all the keys of object.

Then you can use indexing like Object.keys(objectName)[0] to get the key of first element:

Javascript Object.keys method

The for. in Loop

The second method is for. in loop. Try it and break after the first iteration so as to get the first key of the object:

for (let prop in object) < // object[prop] break; >

Example:

Javascript for..in loop and break after the first iteration

Object.keys() and for. in

Object.keys() is used to return enumerable properties of a simple array, of an array like an object, and an array like object with random ordering.

Object.keys() returns the array whose elements are strings corresponding to the enumerable properties found upon the object. The property order is similar to that given by the object manually in a loop applied to the properties.

The for. in loop iterates over «enumerable» properties of the object and applies to all objects that have these properties. An enumerable property is the property of an object that has an Enumerable value of true.

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