JavaScript Code Typing

Optional Chaining & Nullish

?. ?? and ??= plus the ?.[] and ?.() call forms

Spread & Rest

Three dots across arrays, objects, rest params, and defaults

Template Literals

Backticks, ${} interpolation, multiline blocks, and tagged templates

Destructuring & Computed Keys

Nested patterns, defaults, renames, and obj[key] access

Checkpoint: Symbol Fluency

Every JavaScript glyph cluster from this module in one longer drill

Keywords

Reserved words grouped and repeated for rhythm

Declarations

const, let, arrow functions, and classes

ESM Imports & Exports

import, export, default, aliases, and dynamic import

async / await

await, for await, and the Promise combinators

Idiomatic One-Liners

map, filter, reduce, spread, and nullish patterns

Array Method Chains

map, filter, reduce, flatMap, at, and sort comparators

Checkpoint: Keywords & Idioms

Modules, async, and array idioms inside one exported helper

Control Flow

if/else, for-of, while, and switch in realistic shapes

Functions & Methods

Arrow params, destructuring, defaults, and async/await

Class with Private Fields

ES class syntax with #private state, getters, and toJSON

Error Handling

Custom Error subclasses with try/catch and Promise.allSettled

Map & Set Collections

Tallying with Map, deduping with Set, grouping with Object.groupBy

Realistic Snippet

Fetch a JSON feed, rank it, and render to the DOM

Event Delegation

One document listener routing clicks through data attributes

Checkpoint: Real Snippets

A fetch wrapper with AbortController timeouts and retries

Speed Run: Debounce & Throttle

Two closure-based timer utilities typed without stopping

Speed Run: LRU Cache

Map insertion order used as an eviction policy

Speed Run: Form Validation

A rule table reduced into a field-error map

Speed Run: Array Pipeline

groupBy, sum, and sort chained over an order list

Speed Run: Test Suite

node:test and assert wrapped around a slugify helper

Checkpoint: Sustained Speed

An event-latency report typed in one continuous run

Assessment Sim 1: Customer Revenue Report

A cached fetch, a groupBy, and a ranked payout table

Assessment Sim 2: Log Analyzer

A complete ranked-table program over request records

Assessment Sim 3: Paginated Fetch

A full page loop with exponential backoff and retries

Assessment Sim 4: Task Store

An add/complete/query store persisted with node:fs/promises

Checkpoint: JavaScript Mastery Final

An end-to-end priced order report -- the course's graded final