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JavaScript Objects Cheat Sheet

JavaScript Objects Cheatsheet

Action Code Example
Create an object const user = { name: 'Alice', age: 30 };
Access property user.name or user['name']
Update property user.age = 31;
Add new property user.email = 'a@example.com';
Delete property delete user.email;
Check if property exists 'name' in user or user.hasOwnProperty('name')
Loop through keys for (let key in user) { console.log(key); }
Loop through key-values Object.entries(user).forEach(([k, v]) => console.log(k, v));
Get all keys Object.keys(user)
Get all values Object.values(user)
Get key-value pairs Object.entries(user)
Shallow copy const clone = { ...user }; or Object.assign({}, user)
Deep copy const deepClone = JSON.parse(JSON.stringify(user));
Merge objects const merged = { ...obj1, ...obj2 };
Freeze (make read-only) Object.freeze(user)
Seal (no new props) Object.seal(user)
Convert to JSON JSON.stringify(user)
Parse from JSON JSON.parse(jsonString)