Objects
Model related data with properties, methods, destructuring, and safe copies.
Objects group named values. They model records such as a learner, lesson, settings object, or API response.
Create and read properties
lesson.js
const lesson = {
title: "Objects",
minutes: 12,
complete: false,
markComplete() {
this.complete = true;
},
};
console.log(lesson.title);
console.log(lesson["minutes"]);
Dot notation is clearest for known property names. Bracket notation accepts a computed key.
Destructure and copy
updates.js
const { title, minutes = 0 } = lesson;
const completedLesson = { ...lesson, complete: true };
Object spread makes a shallow copy and later properties override earlier ones. Nested objects still share references.
Inspect an object
entries.js
const scores = { html: 90, css: 84, javascript: 88 };
for (const [course, score] of Object.entries(scores)) {
console.log(`${course}: ${score}`);
}
Object.keys, Object.values, and Object.entries turn an object's own enumerable properties into arrays.
Keep this
Use objects for named records, choose clear access syntax, understand shallow copying, and validate external shapes.
学习位置已保存在此设备上。