TypeScript - Tech Ladder

TypeScript Progression Ladder

The TypeScript progression ladder is a grouping of concepts and skills relevant to TypeScript programming. It provides aspiring TypeScript programmers with a way to track and improve their TypeScript skills.

novice

CONCEPTS

SKILLS

RESOURCES

COMPLETED

Type inference

Understand how TS automatically identifies the type of a variable or object

Type annotations

Declare the types of a variable or object when the type inference system is not enough

Primitive types

Declare and work with basic types

Non-nullable types

Avoid potential error by making null and undefined explicit

Structural type system

Understand the difference with a nominal type system and the type compatibility rules

Function declarations & function expressions

Understand the differences between function expressions and declarations

Enumerations

Avoid magic strings and code duplication

Object literals

Declare and work with object instances

Arrays

Declare and work with arrays

Tuples

Declare and work with tuples

Interfaces

Declare and work with interfaces

Classes

Declare and work with classes

Modules

Organize code bases

Namespaces

Declare and work with namespaces

Triple-Slash Directives

Include additional type definition files in the compilation process

String templates & tagged templates

Generate new strings at runtime

advanced_beginner

CONCEPTS

SKILLS

RESOURCES

COMPLETED

Local types

Declare local classes, interfaces, enums, and type aliases

Ambient declarations

Work with existing JavaScript libraries and APIs

Scope and hoisting

Prevent issues by limiting the scope of variables

Type assertions and casting

Change the type of a variable or object

Function types

Declare the type of functions such as callbacks

Arrow functions

Prevent issues with the this operator

Optional and default parameters

Declare optional and default function arguments

Rest parameters

Declare functions with an arbitrary number of arguments

Destructuring assignment

Extract variables from the properties of an object

Union types

Declare wider types from existing types

Intersection types

Declare narrower types from existing types

Type aliases

Declare aliases for existing types

Literal types

Narrow down primitive types to concrete values such as object keys

Control-flow analysis

Understand how TypeScript narrows down a given types

Type guards

Have control over how the TypeScript compiler narrows down a given type

The never type

Detect dead end code paths and unnecessary type guards

The unknown type

Prevent errors by making uncertainty explicit

Readonly

Prevent issues by avoiding property mutations

Strict property initialization

Prevent errors by ensuring that classes are correctly initialized

Inheritance

Re-use code by extending existing classes

Mixins

Take advantage situations in which multiple inheritance is safe

Abstract classes

Reuse code using abstract classes

competent

CONCEPTS

SKILLS

RESOURCES

COMPLETED

Built-in type declarations (lib.d.ts)

Avoid re-declaring existing JavaScript APIs

Index signature

Type-safe property access by index

Weak types

Prevent adding wrong properties to objects with optional properties

Function overloading

Create multiple functions of the same name with different arguments

Closures

Implement higher-order functions

Prototypes

Understand how objects and inheritance work at runtime

The this operator

Prevent and understand potential runtime issues

Generic types

Avoid type assertions in re-usable code

Generic defaults

Avoid empty object as the default value for generic parameters

Generic constraints

Limit the types that can be used as a generic parameter

Custom type guards

Narrow down union types

Promises

Avoid callback hells and gain more control over asynchronous operations

Async/await

Write asynchronous code that looks synchronous

Decorators

Implement the decorator pattern and declare metadata for libraries and tools

Symbols

Declare unique identifiers at runtime

JSX

Understand the template systems of UI libraries such as React

Discriminated unions

Narrow down union types using literal types

proficient

CONCEPTS

SKILLS

RESOURCES

COMPLETED

The keyof operator

Extract the keys of an object as literal types

Lookup types

Use literal types and index types to extract the type of a property of a given type

Polymorphic this type

Express hierarchical fluent interfaces with ease

Mapped types

Map the type of all the properties in an object to a different type

Built-in mapped types

Avoid re-declaring existing mapped types

Conditional types

Map the type of some of the properties in an object to a different type

Built-in conditional types

Avoid re-declaring existing conditional types

The infer keyword

Extract types from existing types such as the value of an element in an array or the return in a function

Generators (function*)

Declare functions that can be exited and later re-entered

Asynchronous generators and iterators (for await … of)

Iterate collections for asynchronous values

Delegating to another generator (yield*)

Implement sagas and other advances asynchronous programming patterns

Type Checking JavaScript Files

Find type errors in JavaScript files

Function, bind, call and apply

Partially apply functions

The JavaScript event loop

Understand potential complex runtime and performance issues

expert

CONCEPTS

SKILLS

RESOURCES

COMPLETED

Module resolution rules

Understand how TypeScript resolves modules

Implement type definitions

Create type definitions when they are not available

Compiler internal APIs

Create code analysis tools and contribute to the compiler

Language services APIs

Create code analysis tools and IDE plugins

Path mapping

Simplify refactoring of directories in large projects

Project references

Faster build for large projects and monorepos

Please note: some of the preceding topics such as promises are not only relevant to TypeScript (as they are also relevant to JavaScript). These topics have been included because we assume that a novice reader has no previous experience with both JavaScript and TypeScript

This is a community-driven document, please share your feedback, help us to improve it. Please open an issue or send us a PR on Github!

TypeScript Progression Ladder

The TypeScript progression ladder is a grouping of concepts and skills relevant to TypeScript programming. It provides aspiring TypeScript programmers with a way to track and improve their TypeScript skills.

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