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JavaScript Coding Conventions
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‎JavaScript Coding Conventions

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# JavaScript Coding Conventions
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| Object Name | Notation | Length | Plural | Prefix | Suffix | Abbreviation | Char Mask |Underscores |
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| ------------------------- | ---------- | ------ | ------ | ------ | ------ | ------------ | -------------------|-------------|
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| Function name | PascalCase | 50 | Yes | No | Yes | Yes | [A-z][0-9] | No |
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| Function arguments | CamelCase | 50 | Yes | No | No | Yes | [A-z][0-9] | No |
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| Local variables | CamelCase | 50 | Yes | No | No | Yes | [A-z][0-9] | No |
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| Constants name | PascalCase | 50 | Yes | No | No | Yes | [A-z][0-9] | No |
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| Field name | CamelCase | 50 | Yes | No | No | Yes | [A-z][0-9] | No |
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***
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Coding conventions are style guidelines for programming. They typically cover:
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1. Naming and declaration rules for variables and functions.
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1. Rules for the use of white space, indentation, and comments.
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Coding conventions secure quality:
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1. Improves code readability
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1. Make code maintenance easier
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***
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Always use the same naming convention for all your code. For example:
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***
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1. Do use camelCasing for variable and function arguments names;
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2. Do use PascalCasing for function names and global variable;
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3. Constants (like PI) written in UPPERCASE;
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4. Do not use under_scores in variable, constants, function arguments or function names;
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5. Do not use hyphens in JavaScript names.
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***
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#### Naming Conventions
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Do use PascalCasing for function names:
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function HelloWorld()
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{
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}
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Do use camelCasing for function arguments and local variables:
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function Hello(isShow)
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{
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}
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firstName = "John";
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lastName = "Doe";
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price = 19.90;
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discount = 0.10;
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fullPrice = price * 100 / discount;
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***Note: Don't start names with a $ sign. It will put you in conflict with many JavaScript library names.***
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#### Spaces Around Operators
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Always put spaces around operators ( = + / * ), and after commas:
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Examples:
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var x = y + z;
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var values = ["Volvo", "Saab", "Fiat"];
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#### Code Indentation
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Always use 4 spaces for indentation of code blocks:
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Functions:
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function ToCelsius(fahrenheit)
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{
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return (5/9) * (fahrenheit-32);
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}
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***Note: Do not use tabs (tabulators) for indentation. Text editors interpret tabs differently.***
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#### Statement Rules
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*General rules for simple statements: Always end simple statement with a semicolon.*
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Examples:
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var values = ["Volvo", "Saab", "Fiat"];
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var person = {
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firstName: "John",
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lastName: "Doe",
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age: 50,
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eyeColor: "blue"
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};
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#### General rules for complex (compound) statements:
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***
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1. Put the opening bracket at the end of the first line.
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2. Use one space before the opening bracket.
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3. Put the closing bracket on a new line, without leading spaces.
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4. Do not end complex statement with a semicolon.
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***
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Functions:
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function toCelsius(fahrenheit) {
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return (5/9) * (fahrenheit-32);
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}
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Loops:
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for (i = 0; i < 5; i++) {
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x += i;
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}
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Conditionals:
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if (time < 20) {
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greeting = "Good day";
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} else {
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greeting = "Good evening";
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}
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#### Object Rules
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General rules for object definitions:
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***
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1. Place the opening bracket on the same line as the object name.
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2. Use colon plus one space between each property and it's value.
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3. Use quotes around string values, not around numeric values.
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4. Do not add a comma after the last property-value pair.
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5. Place the closing bracket, on a new line, without leading spaces.
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6. Always end an object definition with a semicolon.
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***
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Example:
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var person = {
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firstName: "John",
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lastName: "Doe",
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age: 50,
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eyeColor: "blue"
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};
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Short objects can be written compressed, on one line, like this:
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var person = {firstName:"John", lastName:"Doe", age:50, eyeColor:"blue"};
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***Line Length < 80***
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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.
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Example:
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document.getElementById("demo").innerHTML = "Hello World.";
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#### Loading JavaScript in HTML
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Use simple syntax for loading external scripts (the type attribute is not necessary):
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<script src="myscript.js">
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#### Accessing HTML Elements
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A consequence of using "untidy" HTML styles, might result in JavaScript errors. These two JavaScript statements will produce different results:
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var obj = getElementById("Demo")
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var obj = getElementById("demo")
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*If possible, use it naming convention (as JavaScript) in HTML.*
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#### File Extensions
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1. HTML files should have a .html extension (not .htm);
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2. CSS files should have a .css extension;
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3. JavaScript files should have a .js extension.
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## Offical Reference
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1. [Google JavaScript Style Guide](http://google-styleguide.googlecode.com/svn/trunk/javascriptguide.xml)
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2. [JavaScript Style Guide and Coding Conventions](http://www.w3schools.com/js/js_conventions.asp)

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