Object entries in Javascript - Step-by-Step Execution

Concept Flow - Object entries

Start with an object

↓

Call Object.entries(obj)

↓

Iterate over each key-value pair

↓

Create array of [key, value

↓

Return the array

This flow shows how Object.entries takes an object and returns an array of key-value pairs.

Execution Sample

Javascript

const obj = {a: 1, b: 2};
const entries = Object.entries(obj);
console.log(entries);

This code converts an object into an array of its key-value pairs and prints it.

Execution Table

Step	Action	Object State	Result	Output
1	Define obj	{a: 1, b: 2}	Object created
2	Call Object.entries(obj)	{a: 1, b: 2}	Array of entries created	[['a', 1], ['b', 2]]
3	Print entries	[['a', 1], ['b', 2]]	Output to console	[['a', 1], ['b', 2]]

💡 All object entries processed and output printed.

Variable Tracker

Variable	Start	After Step 1	After Step 2	Final
obj	undefined	{a: 1, b: 2}	{a: 1, b: 2}	{a: 1, b: 2}
entries	undefined	undefined	[['a', 1], ['b', 2]]	[['a', 1], ['b', 2]]

Key Moments - 3 Insights

Why does Object.entries return an array of arrays instead of an object?

Object.entries returns an array because it represents each key-value pair as a two-element array, making it easy to iterate over with loops like for...of. This is shown in execution_table step 2 where the result is an array of [key, value] pairs.

Does Object.entries include inherited properties?

No, Object.entries only includes the object's own enumerable properties, not inherited ones. This is why the object state in execution_table step 1 matches exactly the entries in step 2.

What happens if the object is empty?

If the object is empty, Object.entries returns an empty array. This means no entries to iterate over, similar to execution_table but with an empty result array.

Visual Quiz - 3 Questions

Look at the execution_table, what is the value of 'entries' after step 2?

A [['a', 1], ['b', 2]]

B {a: 1, b: 2}

C undefined

D ['a', 'b']

💡 Hint

Check the 'Result' and 'Output' columns in execution_table row for step 2.

At which step is the array of key-value pairs created?

A Step 1

B Step 3

C Step 2

D Never

💡 Hint

Look at the 'Action' and 'Result' columns in execution_table to find when Object.entries is called.

If the object had an inherited property, would it appear in the entries array?

A Yes, all properties appear

B No, only own enumerable properties appear

C Only inherited properties appear

D Only non-enumerable properties appear

💡 Hint

Refer to key_moments about inherited properties and execution_table step 2.

Concept Snapshot

Object.entries(obj) returns an array of [key, value] pairs from obj.
Only own enumerable properties are included.
Useful for looping over object entries.
Result is an array of arrays.
Example: {a:1} → [['a',1]]

Full Transcript

We start with an object that has some properties. When we call Object.entries on it, JavaScript creates an array where each element is a two-item array: the key and its value. This array is easy to loop over or use in other array methods. The entries only include the object's own properties, not those inherited from its prototype. Finally, printing the entries shows the array of key-value pairs.