Arrays & Objects

Objects

An object groups related values under named keys (also called properties).

const course = {
  title: "JavaScript Essentials",
  lessons: 16,
  free: true,
  tags: ["web", "beginner"],
  describe() {
    return `${this.title} has ${this.lessons} lessons`;
  },
};

console.log(course.title);        // dot notation
console.log(course["lessons"]);   // bracket notation
course.level = "Beginner";        // add a property
delete course.free;               // remove one
console.log(course.describe());

Output

JavaScript Essentials
16
JavaScript Essentials has 16 lessons

Object.keys(course);    // ["title", "lessons", ...]
Object.values(course);
Object.entries(course); // [["title", "..."], ...]