fix: correct typos

[cfigueiroa]

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[github-actions]

Thanks for the PR!

This section of the codebase is owned by @khaosdoctor and @danilofuchs - if they write a comment saying "LGTM" then it will be merged.

[github-actions]

Translation of TS for the New Programmer.md

---

title: TypeScript for the New Programmer
short: TS for the New Programmer
layout: docs
permalink: /pt/docs/handbook/typescript-from-scratch.html

oneline: Learn TypeScript from scratch

Congratulations on choosing TypeScript as one of your first languages - you're already making good decisions!

You may have heard that TypeScript is a "flavor" or a "variant" of JavaScript. The relationship between TypeScript (TS) and JavaScript (JS) is unique among modern programming languages, so learning more about this relationship will help you understand how TypeScript adds to JavaScript.

What is JavaScript? A Brief History

JavaScript (also known as ECMAScript) began its life as a simple scripting language for browsers. At the time it was invented, it was always expected to be used for small snippets of code embedded on a web page - writing more than a dozen lines of code would be unusual. Therefore, young browsers of the time executed such code very slowly. However, over time, JS became more and more popular and web developers began using it to create interactive experiences.

Web browser developers responded to this increased use of JS by optimizing their engines by optimizing their engines (dynamic compilation) and extending what could be done with it (adding APIs), which in turn made web developers use it even more. On modern websites, your browser is often running applications that have hundreds of thousands of lines of code. This is the long and gradual growth of the web, starting as a simple network of static pages and evolving into a platform for Applications rich of all kinds.

More than that, JS has become popular enough to be used outside the context of browsers, such as implementing JS servers using node.js. JS's "run anywhere" nature makes it an attractive choice for cross-platform development. There are many developers these days who use only JavaScript to program your entire suite of applications!

To summarize, we have a language that was developed for quick uses and then grew into a complete tool for writing applications with millions of lines. Every language has its own Individuals - uniqueness and surprises and the humble beginning of JavaScript makes it many These. Some examples:

• The JavaScript equality operator (==) coage their arguments, leading to unexpected behavior:

  if ('' == 0) {
  	// É! mas porque??
  }
  if (1 < x < 3) {
  	// Verdadeiro para qualquer valor de x!
  }

• JavaScript also allows you to access properties that are not present:

  const obj = { width: 10, height: 15 };
  // Porque isso é NaN? Ortografia é difícil!
  const area = obj.width * obj.heigth;

Most programming languages would throw an error when this type of situation occurred, some would do so at compile time - before any code was running. When writing small programs, such individualities are annoying but manageable; when writing applications with hundreds or thousands of lines of code, these constant surprises are a serious problem.

TypeScript: A Static Type Checker

We said before that some languages would not allow these programs to bug or run. Error detection without code execution is called static check. Determining what is an error and what is not based on the types of values being operated is called static verification of Types.

TypeScript checks a program for errors before it runs and does so based on the kinds of values, is a static type tester. For example, the last example above has an error because of the kind from obj. Here's the error that TypeScript encounters:

// @errors: 2551
const obj = { width: 10, height: 15 };
const area = obj.width * obj.heigth;

A JavaScript Typed Superset

How does TypeScript re-trigger with JavaScript then?

Syntax

TypeScript is a language that is a Superset of JavaScript: JS syntax is therefore valid in TS. Syntax refers to the way we write text to form a program. For example, this code has a syntax because there's a lack of ):

// @errors: 1005
let a = (4

TypeScript does not consider any JavaScript code to be an error because of its syntax. This means you can take any JavaScript functional code and put it into a TypeScript file without worrying about how it's written.

Types

However, TypeScript is a superset Typed, meaning that you add rules about how different types of values can be used. The previous error about obj.heigth it wasn't a mistake of syntax: is an error in the use of a value type (a kind) in an incorrect manner.

As another example, this is JavaScript code that you can run in your browser and it will display a value:

console.log(4 / []);

This syntactically cool program displays Infinity. TypeScript in turn considers splitting a number by an array a meaningless operation and will display an error:

// @errors: 2363
console.log(4 / []);

It's possible that you actually Want divide a number by an array, maybe just to see what happens, but most of the time this is a programming error. The TypeScript type checker is designed to allow correct programs while preventing as many common errors as possible. (Later, we'll learn about settings that you can use to configure how strictly TypeScript checks your code.)

If you move some code from a JavaScript file to a TypeScript file, you can see type errors depending on how the code is written. These can be legitimate problems with code or TypeScript being overconservative. Through this guide we will demonstrate how to add various TypeScript syntaxes to eliminate such errors.

Runtime Behavior

TypeScript is also a programming language that preserves the runtime behavior javascript. For example, dividing by zero in JavaScript produces Infinity rather than throwing an error at run time. As a principle, TypeScript never changes the comporance of javascript code runtime.

This means that you move JavaScript code from TypeScript, it is secure that will run the same way that TypeScript thinks the code has type errors.

Maintaining the same behavior at runtime as JavaScript is a fundamental promise of TypeScript because it means that you can easily transition between two languages without worrying about subtle differences that can cause your program to stop working.

Deleted Types

Roughly speaking, once the TypeScript compiler has finished checking your code, it Erases the types to produce the resulting "compiled" code. This means that once your code is compiled, the pure Result JS code has no type information.

This also means that TypeScript never changes the behaviour program based on the types it infers. The end of this is that while you see type errors during compilation, the type system itself has no influence on how your program works when it runs.

Finally, TypeScript does not provide any additional runtime library. Your programs will use the same standard (or external) libraries as JavaScript programs, so there are no additional TypeScript-specific tools to learn.

Learning JavaScript and TypeScript

We often see the question "Should I learn JavaScript or TypeScript?".

The answer is that you can't learn TypeScript without learning JavaScript! TypeScript shares syntax and runtime behavior with JavaScript, so anything you want to learn about JavaScript will be helping you learn TypeScript at the same time.

There are many, many features available for programmers to learn JavaScript; you No you should ignore these features if you are writing TypeScript. For example, there are about 20 times as many questions in StackOverflow that are marked with javascript than with typescriptbut All the issues javascript also apply to TypeScript.

If you find yourself looking for something like "how to organize a list in TypeScript," remember: TypeScript is the JavaScript execution environment with build-time type checker. The way you organize a list in TypeScript is the same in JavaScript. If you find a feature that uses TypeScript directly this is great too, but don't just think that you need specific TypeScript answers to day-to-day questions about how to achieve execution environment tasks.

Next Steps

This was a short summary of the syntax and tools used in TypeScript in day-to-day life. From here, you can:

• Learning some fundamentals of JavaScript, we recommend:

  • Microsoft's JavaScript Resources OR
  • JavaScript guide at the Mozilla Web Docs

• Continue to TypeScript for JavaScript programmers

• Read the full Handbook from start to finish (30m)

• Explore the Playground examples

Generated by 🚫 dangerJS against d4e6eb7

[danilofuchs]

LGTM

[danilofuchs]

Hi @cfigueiroa, for some reason the branch was not merged by the bot.
Can you recreate the branch please?

[cfigueiroa]

Hi @cfigueiroa, for some reason the branch was not merged by the bot. Can you recreate the branch please?

done

[danilofuchs]

LGTM

[github-actions]

Merging because @danilofuchs is a code-owner of all the changes - thanks!