JavaScript Object Exercises
Master JavaScript objects with interactive exercises covering properties, bracket notation, nested objects, destructuring, spread, Object.entries, copying, and data transformation. Write and test real code in your browser with immediate feedback.
Exercises
Work from beginner to very hard, or use the filters to find a specific skill.
Object Literals
An object literal groups related values under property names. The object becomes...
Bracket Notation
Dot notation reads a property whose name is written directly in the code. Bracke...
Property Updates
A `const` object variable keeps pointing at the same object, but the object's pr...
Nested Objects
Objects can contain other objects. Reading nested data means following the path ...
Reading Object Properties
JavaScript functions often receive one object instead of several values, so reus...
Computed Property Names
An object literal can use a value as a property name. Square brackets inside the...
Destructuring Defaults
Object destructuring pulls named properties into local variables. A default valu...
Object Spread Copies
Object spread copies the own enumerable properties from one object into another ...
Optional Chaining
Nested object reads fail when an intermediate value is `null` or `undefined`. Op...
Lookup Objects
Practice JavaScript object indexing by turning an array of records into direct i...
Frequency Objects
Practice JavaScript objects as frequency tables by counting ticket statuses unde...
Nested Object Copies
Practice JavaScript object spread by updating a nested preferences value through...
Object Rest
Practice JavaScript object rest syntax by removing known private fields while ke...
Object.entries
Practice JavaScript Object.entries by converting request parameters into a sorte...
Object Path Reading
Practice JavaScript object path reading by walking nested data from an array of ...
Nested Object Merging
Practice JavaScript nested object merging by combining defaults with user overri...
Nested Grouping
Practice JavaScript object grouping by building role-based arrays from project m...
Inverting Object Maps
Practice JavaScript object inversion by grouping original keys under the values ...
Practice JavaScript objects with real data
Objects group related values under named properties, making them useful for representing users, products, settings, API responses, and other application data. These JavaScript object exercises help you create, read, update, copy, and transform those structures while keeping the shape of the data visible.
The collection progresses from object literals, dot and bracket notation, property updates, and nested objects into computed keys, destructuring defaults, object rest and spread, Object.entries, lookup tables, frequency objects, grouping, merging, and object maps.
Later challenges focus on the decisions that matter in real applications: choosing a safe access pattern, avoiding accidental mutation, understanding shallow copies, reading nested paths, comparing records, and cloning plain data. That makes the practice useful for configuration data, application state, and structured responses rather than isolated syntax drills.
- Exercises
- 20
- Difficulty
- Beginner to Very Hard
- Good to know first
- Know how to declare variables and call functions; basic array familiarity is helpful for entry methods and grouped data.
What you’ll practice
- Create objects and read properties with dot or bracket notation
- Add, update, and work with nested object properties
- Build dynamic records with computed property names
- Extract values with object destructuring and defaults
- Copy and omit properties with object spread and rest
- Iterate through records with Object.entries
- Build lookup, frequency, grouping, and inverted object maps
- Merge, compare, and clone structured object data
Who these exercises are for
This practice set starts with beginner-friendly object basics and grows into harder data-manipulation challenges. It suits learners meeting JavaScript objects for the first time, students reinforcing a course, and developers who want more confidence working with structured application data.
How practice works
- Write and run JavaScript directly in your browser
- Use instant test feedback to catch access and mutation mistakes
- Progress from beginner object literals to deep cloning and diffs
- Filter exercises by difficulty and save your progress when signed in