2nd Theoretical Class: JavaScript Essentials for React

Variable declarations

Use only if necessary => Use .
Don't use !

Template literals

Strings delimited with (backticks) allowing for multi-line strings and string interpolation

• can contain any expression

Destructuring

Unpack properties from an object or items from an array into constants.

Object destructuring

Useful features of this syntax:

• rename destructured properties
• set default values of properties which are undefined

Array destructuring

Rest & Spread operator ()

The operator can collect or expand values.

Expanding (spread)

Collecting (rest)

Optional chaining

Access a property of an object which is or

Arrow function

An alternative way of declaring a function

Arrow functions are useful for passing anonymous callback functions - see below.

Array method

Transform each element in an array using a callback function

• a new array is created and the original array is not modified

Module imports/exports

Ways to split your application into smaller modules

Default import

• only one default import in a file
• imported name can be anything

Named imports

• multiple imports in one file
• imported name is always the same as the exported name

Resources

• Template literals (Template strings)
• Destructuring assignment
• Spread/rest operator
• Optional chaining (?.)
• Arrow function expressions
• Array.prototype.map
• JavaScript modules