Learning overview
- Estimated time
- 4 minutes
- Difficulty
- Beginner
- Prerequisites
- No prior experience required
- Learning outcome
- Explain javascript using a clear mental model · Apply javascript in practical JavaScript work
- Last updated
- July 18, 2026
Model records with named properties
Use dot notation for known valid identifiers and bracket notation for computed keys. Destructuring extracts values into local bindings and can provide defaults when a property is undefined.
const course = {
id: "javascript",
title: "JavaScript Fundamentals",
stats: { lessons: 24, completed: 8 },
};
const { title, stats: { completed = 0 } } = course;
const field = "title";
console.log(course[field]);Understand identity and shallow copies
Two separately created objects are not strictly equal even when their properties match. Assignment copies a reference, while spread creates a new outer object and preserves references to nested values.
const updated = {
...course,
stats: {
...course.stats,
completed: course.stats.completed + 1,
},
};
console.log(updated !== course); // true
console.log(updated.stats !== course.stats); // trueRecognize prototype delegation
When an object lacks an own property, JavaScript may look up its prototype chain. Class syntax builds on this delegation model. Prefer composition and plain data objects unless shared prototype behavior provides a clear benefit.
Frequently asked questions
Why are two identical JavaScript objects not equal?
Strict equality compares object identity, not a recursive comparison of properties. Two object literals create two distinct identities.
When should I use Map instead of an object?
Use Map when keys are not limited to strings and symbols, insertion order and size are central, or frequent dynamic key operations benefit from its dedicated API.
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