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Object.keys, values, entries

JavaScript provides three essential methods to extract data from objects in different formats:

  • Object.keys(obj) – Returns an array of the object’s own enumerable property names (keys).
  • Object.values(obj) – Returns an array of the object’s own enumerable property values.
  • Object.entries(obj) – Returns an array of [key, value] pairs from the object.
Summary of Object Methods
MethodReturns
Object.keys(obj)Array of keys (strings)
Object.values(obj)Array of values
Object.entries(obj)Array of [key, value] pairs (arrays)

📌 Deep Dive: Extracting Keys, Values, and Entries

JAVASCRIPT
const user = {
  name: "Alice",
  age: 25,
  active: true
};

console.log(Object.keys(user));    // ["name", "age", "active"]
console.log(Object.values(user));  // ["Alice", 25, true]
console.log(Object.entries(user)); // [["name", "Alice"], ["age", 25], ["active", true]]
Output
["name", "age", "active"]
["Alice", 25, true]
[["name", "Alice"], ["age", 25], ["active", true]]

These methods are very useful for:

  • Iterating over object properties using loops (e.g., for...of or forEach).
  • Transforming objects into arrays for data manipulation.
  • Converting objects to other formats, like Maps or JSON.

📌 Deep Dive: Looping Through Object with Object.entries()

JAVASCRIPT
const scores = { alice: 80, bob: 90, charlie: 70 };

for (const [name, score] of Object.entries(scores)) {
  console.log(`${name} scored ${score}`);
}
Output
alice scored 80
bob scored 90
charlie scored 70
Illustration of object_keys_values_entries
Illustration of object_keys_values_entries

💡 Remember:

These methods only include the object’s own enumerable properties; inherited or non-enumerable properties are excluded.

⚠️ Important:

The order of keys, values, and entries is the same and corresponds to the order of the properties in the object, which generally follows creation order for string keys.

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