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Always use the same coding conventions for all your JavaScript projects.
Coding conventions are style guidelines for programming.
Naming and declaration rules for variables and functions. Rules for the use of white space, indentation, and comments. Programming practices and principles.
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.
At W3schools we use camelCase for identifier names (variables and functions). All names start with a letter. At the bottom of this page, you will find a wider discussion about naming rules.
firstName = "John";
lastName = "Doe";
price = 19.90;
tax = 0.20;
fullPrice = price + (price * tax);Always put spaces around operators ( = + - * / ), and after commas:
let x = y + z;
const myArray = ["Volvo", "Saab",
"Fiat"];Always use 2 spaces for indentation of code blocks:
function toCelsius(fahrenheit) {
return (5 / 9) * (fahrenheit - 32);
}
Do not use tabs (tabulators) for indentation. Different editors interpret tabs differently.Always end a simple statement with a semicolon.
const cars = ["Volvo", "Saab",
"Fiat"];
const person = {
firstName: "John", lastName: "Doe", age: 50, eyeColor:
"blue"
};
General rules for complex (compound) statements:Put the opening bracket at the end of the first line. Use one space before the opening bracket. Put the closing bracket on a new line, without leading spaces. Do not end a complex statement with a semicolon.
function toCelsius(fahrenheit) {
return (5 / 9) * (fahrenheit - 32);
}for (let i = 0; i < 5; i++) {
x += i;
}if (time < 20) {
greeting = "Good day";
} else {
greeting = "Good evening";
}Place the opening bracket on the same line as the object name. Use colon plus one space between each property and its value. Use quotes around string values, not around numeric values.
Formula
Do not add a comma after the last property - value pair.Place the closing bracket on a new line, without leading spaces. Always end an object definition with a semicolon.
const person = {
firstName: "John", lastName: "Doe", age: 50, eyeColor:
"blue"
};Short objects can be written compressed, on one line, using spaces only between properties, like this:
const person = {firstName:"John", lastName:"Doe", age:50, eyeColor:"blue"};Formula
Line Length < 80
For readability, avoid lines longer than 80 characters.
If a JavaScript statement does not fit on one line, the best place to break it, is after an operator or a comma.document.getElementById("demo").innerHTML =
"Hello Dolly.";Always use the same naming convention for all your code. For example: