オブジェクトプロパティのドット表記とブラケット表記 – 違いは何ですか?

Dot Notation

Dot notation is simpler and more readable. It's used when:

1. The property name is a valid identifier (contains only letters, digits, $, or _, and doesn’t start with a digit).
2. You know the property name ahead of time.

For example:

const person = { name: 'alice', age: 30 };
console.log(person.name); // 'alice'

Bracket Notation

Bracket notation is more flexible and allows you to:

1. Use property names stored in variables.
2. Access properties with special characters, spaces, or numbers that aren’t valid identifiers.
3. Dynamically build property names at runtime.

Examples:
1. Using variables to access properties:

const person = { name: 'alice', age: 30 };
const prop = 'name';
console.log(person[prop]); // 'alice'

2.Properties with special characters or spaces:

const person = { 'first name': 'alice', age: 30 };
console.log(person['first name']); // 'alice'

3.Dynamically generated property names:

const property = 'name';
console.log(person[property]); // 'alice'

When to Use Bracket Notation

• If the property name is dynamic or stored in a variable.
• If the property name has spaces, special characters, or starts with a number.

For most other cases, dot notation is preferred because it’s more readable and concise.

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