JavaScript Getting Started: Environment Construction and Data Types

This article will guide you to build a JavaScript development environment and introduce the basic data types in JavaScript. You can use your browser or Node.js for code testing.

Environmental construction

The most convenient way is to use your browser. If you are new to programming, this is ideal. Simply press Ctrl Shift K in Firefox, or Ctrl Shift J in Chrome, to open the browser console and start writing and running the code. The following figure shows an example of an executed line of code:

If you are familiar with the installation and configuration of the running environment, you can also choose to use Node.js. This will enhance your skills and reflect your technical abilities in your resume.

First of all, you need a text editor to write the code, recommending Sublime Text or Visual Studio Code. Then, download and install Node.js from the official website of Node.js. After the installation is complete, you can verify that the installation is successful by entering a command in the terminal. constThe constants declared by the keyword remain unchanged in the program.

Data type

In programming, you process various types of data, represented by different data types. Each data type has its own operating rules. For example, adding two numbers to get their sum, but adding numbers to strings to get a string.

The following are the main data types in JavaScript:

• Boolean: The value is true or false.
• Symbol: A unique and unchanging key value.
• BigInt: Used to handle large values ??beyond the normal number range.
• Object: Collection of properties.

In addition, there is undefined. The Boolean type represents two values ??of true or false, which is very useful when you only need to determine the true or false. A string (String) is composed of characters, enclosed in single, double, or backquotes. Number type is used to store and manipulate numbers, including positive, negative, and decimal.

The following is an example function that calculates factorial:

function factorial(x) {
  let result = 1;
  while (x > 1) {
    result *= x;
    x -= 1;
  }
  return result;
}

console.log(factorial(5)); // 120
console.log(factorial(10)); // 362880
console.log(factorial(50)); // 3.0414093201713376e+64
console.log(factorial(500)); // Infinity

When calculating a factorial of 500, JavaScript will return Infinity. To handle larger values, you can use the BigInt type:

function factorialBigInt(x) {
  let result = BigInt(1);
  x = BigInt(x);
  while (x > BigInt(1)) {
    result *= x;
    x -= BigInt(1);
  }
  return result;
}

console.log(factorialBigInt(500)); // 正確的500的階乘結果 (一個非常大的BigInt數值)

BigInt type is only applicable to integers and cannot be used for fractional operations. In arithmetic operations, the Number and BigInt types cannot be used in combination.

Object (Object)

Objects in JavaScript are collections of properties, each property is a key-value pair. Functions and arrays are also objects. We will explain objects and arrays in detail in the subsequent tutorial.

Symbol

Symbol() function returns a unique Symbol value. The Symbol.for() method can obtain the same Symbol value based on the key value.

const x = Symbol();
const y = Symbol();

const a = Symbol.for("potato");
const b = Symbol.for("potato");

if (x === y) {
  console.log('Same Symbol');
} else {
  console.log('Symbol Mismatch'); // 輸出此行
}

if (a === b) {
  console.log("This should Match"); // 輸出此行
}

Review

We learned how to build a development environment using Node.js. The first step in programming is to write a problem-solving step, namely the algorithm. The code consists of many statements, which are instructions of the program and are composed of expressions. Expressions can be assigned to variables. Variables are created using the let or const keywords to store various data types.

The subsequent tutorial will explain the conditional statements, allowing you to perform different tasks according to different situations.

Resources

• OneCompiler
• Sublime Text
• Node.js
• ES6 specification
• You Don’t Know JS (You Don’t Know JS)

This article was updated by Monty Shokeen. Monty is a full stack developer who is passionate about writing tutorials and learning new JavaScript libraries.

The above is the detailed content of Learn to Code With JavaScript: Part 1, The Basics. For more information, please follow other related articles on the PHP Chinese website!