You need solid fundamentals in modern JavaScript (ES6+) before Vue will make sense. Vue's reactivity system, component model, and Composition API are all built on core JS concepts. If you skip them, you'll memorize Vue syntax without understanding why things work, and debugging becomes guesswork.

Essential concepts

ES Modules (import/export)

Every Vue file uses modules. You need to understand named vs default exports, re-exports, and how the module system resolves paths.

// Named export
export function useCounter() { /* ... */ }

// Default export
export default { name: 'MyComponent' }

// Importing
import { useCounter } from './composables/useCounter'
import MyComponent from './components/MyComponent.vue'

Destructuring

Used everywhere in Vue: props, composable return values, reactive state.

// Object destructuring
const { name, age } = user
const { data, error } = useFetch('/api/users')

// With defaults
const { page = 1, limit = 20 } = options

// Array destructuring (less common in Vue, but used in some patterns)
const [first, ...rest] = items

Arrow functions

Event handlers, computed properties, watchers, composables all use arrow functions.

const doubled = computed(() => count.value * 2)

watch(source, (newVal, oldVal) => {
  console.log(newVal)
})

const items = users.filter(u => u.active).map(u => u.name)

Understanding this binding matters too. Arrow functions don't have their own this, which is why Vue 3's Composition API avoids this entirely and uses closures instead.

Template literals

Used in dynamic strings, computed messages, and class bindings.

const greeting = computed(() => `Hello, ${user.value.name}!`)
const apiUrl = `/api/users/${userId}/posts`

Spread operator and rest parameters

Props forwarding, merging objects, function arguments.

const defaults = { theme: 'light', lang: 'en' }
const config = { ...defaults, ...userPrefs }

function setup(...args) { /* ... */ }

const newItems = [...items, newItem]

Promises and async/await

Data fetching, API calls, and Nuxt's useFetch all deal with async code.

// Promise chain
fetch('/api/users')
  .then(res => res.json())
  .then(data => console.log(data))
  .catch(err => console.error(err))

// async/await (preferred)
async function loadUsers() {
  try {
    const res = await fetch('/api/users')
    const data = await res.json()
    return data
  } catch (err) {
    console.error(err)
  }
}

Array methods

v-for renders lists, but you manipulate them with array methods: map, filter, find, some, every, reduce, sort, flatMap.

const activeUsers = users.filter(u => u.active)
const names = users.map(u => u.name)
const admin = users.find(u => u.role === 'admin')
const hasAdmin = users.some(u => u.role === 'admin')
const total = items.reduce((sum, item) => sum + item.price, 0)

Optional chaining and nullish coalescing

Safe property access when data might be null (common with API responses).

const city = user?.address?.city
const name = user?.name ?? 'Anonymous'
const count = response?.data?.length ?? 0

Object shorthand and computed properties

Used in reactive objects, component options, and event payloads.

const name = 'Alice'
const age = 30

// Shorthand
const user = { name, age }

// Computed property names
const field = 'email'
const data = { [field]: 'alice@example.com' }

// Shorthand methods
const store = {
  increment() { this.count++ }
}

Important but not urgent

These concepts matter for intermediate/advanced Vue work, but you can learn them alongside Vue:

Closures

The Composition API is built on closures. setup() returns reactive variables that template refs close over.

function useCounter() {
  const count = ref(0)
  function increment() {
    count.value++ // increment closes over count
  }
  return { count, increment }
}

Proxy

Vue 3's reactivity system uses Proxy to intercept property access and mutation. You don't need to write proxies yourself, but understanding the concept helps debug reactivity issues.

const handler = {
  get(target, key) { /* track dependency */ },
  set(target, key, value) { /* trigger effects */ }
}
const proxy = new Proxy(target, handler)

Getters and setters

Computed properties are essentially getters. Writable computed properties use both.

const user = {
  firstName: 'Alice',
  lastName: 'Smith',
  get fullName() {
    return `${this.firstName} ${this.lastName}`
  },
  set fullName(value) {
    const [first, last] = value.split(' ')
    this.firstName = first
    this.lastName = last
  }
}

TypeScript basics

Not required to start, but most Vue 3 projects use TypeScript. Interfaces, generics, and type narrowing become relevant quickly.

What you do NOT need first

• Classes and decorators: Vue 3 doesn't use them. The Options API uses plain objects, the Composition API uses functions.
• Generators and iterators: Rarely used in Vue code.
• WeakMap/WeakSet: Vue uses them internally, but you won't write them yourself.
• Web Components API: Vue components are not web components (unless you explicitly export them as such).

The checklist

Concept	Why it matters for Vue
ES Modules	Every file imports/exports
Destructuring	Props, composable returns, reactive state
Arrow functions	Computed, watchers, event handlers
Template literals	Dynamic strings, URLs
Spread/rest	Object merging, props forwarding
Promises/async-await	Data fetching, API calls
Array methods	List rendering, filtering, transforming
Optional chaining	Safe access to API data
Closures	Composition API is built on them
Proxy (concept)	Understand Vue's reactivity

See also: What is Vue and what are its main features?

References

• JavaScript basics - MDN
• JavaScript modules - MDN
• Introduction - Vue.js docs