How to speed up your JavaScript code.
Loops are often used in programming.
Each statement in a loop, including the for statement, is executed for each iteration of the loop.
Statements or assignments that can be placed outside the loop will make the loop run faster. Continue reading JavaScript Performance
This chapter points out some common JavaScript mistakes.
JavaScript programs may generate unexpected results if a programmer accidentally uses an assignment operator (=), instead of a comparison operator (==) in an if statement. Continue reading JavaScript Common Mistakes
Always use the same coding conventions for all your JavaScript projects.
Coding conventions are style guidelines for programming. They typically cover:
Coding conventions secure quality:
Coding conventions can be documented rules for teams to follow, or just be your individual coding practice.
This page describes the general JavaScript code conventions used by W3Schools.
You should also read the next chapter “Best Practices”, and learn how to avoid coding pitfalls.
Errors can (will) happen, every time you write some new computer code.
Programming code might contain syntax errors, or logical errors.
Many of these errors are difficult to diagnose.
Often, when programming code contains errors, nothing will happen. There are no error messages, and you will get no indications where to search for errors.
Searching for (and fixing) errors in programming code is called code debugging. Continue reading JavaScript Debugging
JSON is a format for storing and transporting data.
JSON is often used when data is sent from a server to a web page.
* The JSON syntax is derived from JavaScript object notation syntax, but the JSON format is text only. Code for reading and generating JSON data can be written in any programming language. Continue reading JavaScript JSON
JavaScript modules allow you to break up your code into separate files.
This makes it easier to maintain a code-base.
Modules are imported from external files with the import statement.
Modules also rely on type="module" in the <script> tag. Continue reading JavaScript Modules
ECMAScript 2015, also known as ES6, introduced JavaScript Classes.
JavaScript Classes are templates for JavaScript Objects.
Use the keyword class to create a class.
Always add a method named constructor() :
class ClassName {
constructor() { ... }
}
class Car {
constructor(name, year) {
this.name = name;
this.year = year;
}
}
The example above creates a class named “Car”. Continue reading JavaScript Classes
Arrow functions were introduced in ES6.
Arrow functions allow us to write shorter function syntax :
let myFunction = (a, b) => a * b;
hello = function() {
return "Hello World!";
}
hello = () => {
return "Hello World!";
}
It gets shorter! If the function has only one statement, and the statement returns a value, you can remove the brackets and the return keyword : Continue reading JavaScript Arrow Function
const person = {
firstName: "John",
lastName : "Doe",
id : 5566,
fullName : function() {
return this.firstName + " " + this.lastName;
}
};
In JavaScript, the this keyword refers to an object. Continue reading JavaScript this Keyword
"use strict"; Defines that JavaScript code should be executed in “strict mode”.
The "use strict" directive was new in ECMAScript version 5.
It is not a statement, but a literal expression, ignored by earlier versions of JavaScript.
The purpose of "use strict" is to indicate that the code should be executed in “strict mode”.
With strict mode, you can not, for example, use undeclared variables. Continue reading JavaScript Use Strict