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.
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.
Always put spaces around operators ( = + - * / ), and after commas:
Always use 4 spaces for indentation of code blocks:
|Do not use tabs (tabulators) for indentation. Different editors interpret tabs differently.|
General rules for simple statements:
General rules for complex (compound) statements:
General rules for object definitions:
Short objects can be written compressed, on one line, using spaces only between properties, like this:
For readability, avoid lines longer than 80 characters.
Always use the same naming convention for all your code. For example:
Should you use hyp-hens, camelCase, or under_scores in variable names?
This is a question programmers often discuss. The answer depends on who you ask:
Hyphens in HTML and CSS:
HTML5 attributes can start with data- (data-quantity, data-price).
CSS uses hyphens in property-names (font-size).
Many programmers prefer to use underscores (date_of_birth), especially in SQL databases.
Underscores are often used in PHP documentation.
PascalCase is often preferred by C programmers.
Use simple syntax for loading external scripts (the type attribute is not necessary):
HTML files should have a .html extension (not .htm).
CSS files should have a .css extension.
Most web servers (Apache, Unix) are case sensitive about file names:
london.jpg cannot be accessed as London.jpg.
Other web servers (Microsoft, IIS) are not case sensitive:
london.jpg can be accessed as London.jpg or london.jpg.
If you use a mix of upper and lower case, you have to be extremely consistent.
If you move from a case insensitive, to a case sensitive server, even small errors can break your web site.
To avoid these problems, always use lower case file names (if possible).
Coding conventions are not used by computers. Most rules have little impact on the execution of programs.
Indentation and extra spaces are not significant in small scripts.
For code in development, readability should be preferred. Larger production scripts should be minified.