How to get Keys, Values, and Entries in JavaScript Object?

For JavaScript Object, in order to get keys, values, and entries we use Object.keys, Object.values, and Object.entries.

• Object.keys(obj) – returns all the keys of object as array
• Object.values(obj) – returns all the values of the object as array
• Object.entries(obj) – returns an array of [key, value]

Let’s say we have a user Object:

let user ={
    name : "Balaji",
    age : 23,
    greet : () => "Hello",
};   

Get Keys of the Object

Use Object.keys to get the keys of the Object:

let keys = Object.keys(user);
keys; //["name", "age", "greet"]

Object.keys will return the keys that are available in the object while calling the function – any new keys added after this will not be updated:

let keys = Object.keys(user);
keys; //["name", "age", "greet"]

user.weight = 65;

// weight key will not be added to keys array 
keys; //["name", "age", "greet"]

Get values of the Object

Use Object.values to get the values of the Object:

let values = Object.values(user);
values; // ["Balaji", 23, ƒ, 65]

Get the entries of the object

Use Object.entries to get the [key, value] pair of the Object:

let entries = Object.entries(user);
entries; 

// output
[ ["name", "Balaji"], ["age", 23], ["greet", ƒ], ["weight", 65] ]

You can use Object.entries to get Object key, value pair, and use array methods like map, filter, and reduce:

let user ={
    name : "Balaji",
    age : 23,
};
let entries = Object.entries(user)
let data = entries.map( ([key, val] = entry) => {
  return `The ${key} is ${val}`;
});
data; //  ["The name is Balaji", "The age is 23"]

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Note:

• When using the Object.keys, symbolic keys are not returned. Instead, use Reflect.ownKeys(obj) to returns all keys; or, use Object.getOwnPropertySymbols to only get symbolic keys.