How to Get the Key List and Length of a JavaScript Object?

How to Retrieve Key List and Length of a JavaScript Object

When working with JavaScript objects, you often need to retrieve the list of keys and their corresponding length. There are several ways to accomplish this.

Using Object.keys()

The Object.keys() method provides a convenient way to obtain an array of all the property keys of an object. It does not include the inherited properties.

Consider the following JavaScript object:

var obj = {
   key1: 'value1',
   key2: 'value2',
   key3: 'value3',
   key4: 'value4'
}

To retrieve the key list and length, you can use the code below:

var keys = Object.keys(obj);
console.log('obj contains ' + keys.length + ' keys: ' + keys);

This will output the following result:

obj contains 4 keys: key1,key2,key3,key4

Other Methods

While Object.keys() is the most commonly used method for retrieving key lists, there are other options:

• Reflect.ownKeys() - Returns an array of all the owned properties (both enumerable and non-enumerable) of an object.
• Object.getOwnPropertyNames() - Returns an array of all the enumerable property names of an object.
• Object.entries() - Returns an array of key-value pairs.

The choice of method depends on your specific requirements. However, Object.keys() is usually the most straightforward and efficient approach.

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