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Coding Guidelines

Table of Contents

General

We use ESLint to lint our Javascript. All basic rules are defined in the .eslintrc file, the most important rules are:

  • Max line length is 80 characters.
  • Indentation is 2 spaces.
  • No multiple empty lines.

We prefer a functional approach and try to use these abstractions over normal control statements. Functions and code must be self-descriptive, use JSDoc blocks only if necessary.

Comments

Rules:

  • Comments must be prefixed with a space sign.
  • The * sign is a exception to the rule.

Examples:

// Single line Comment

//* A Exception to the space rule

/**
* Block Comment
*/

Strings

  • Strings are defined with double quotes.
  • Use template strings if variables are used.

Example:

var string = `Hello ${world}!`;

Variables and Attribute Names

Variable names always use camelCase names, except Constants which use UPPER_CASE. One var, let or const per variable and line.

Examples:

var camelCase = "{value}";
let CamelCase = new Object();
const SOME_CONSTANT = "constant value";

Object Literals

Object literals must have no space after the '{' or before the '}' signs.

Valid Example

var objectLiteral = {"key": "value", "key2": "value2"};

var objectLiteral = {
  "key": "value",
  "key2": "value2",
  "key3": "value3",
  "key4": "value4"
};

Indentation and Line Breaks

Rules:

  • Line breaks are only done if needed.
  • Strings are split at the latest possible position.
    • At the latest whitespace character.
    • The second line is indented with 2 spaces.
      var longString = "A very long string which is longer then one line, which is 80 characters " +
    "in this case. This demonstrates how the second line is indented";
  • Object literals are kept on one line if possible.
    • If the line gets to long put each attribute on a single line.
    • Multi level object literals must be split in to multiple lines.
      • Each level in the object must have 2 spaces as indentation.

Examples:

test(
  "A very long string that is longer then one line, which is 80 characters " +
    "in this case. This demonstrates how the second line is indented.",
  "Another string parameter.",
  {and: "a Literal Object", as: "a parameter", type: "short"}, {
    yet: "another long parameter Object",
    which: "needs to be split in multiple",
    lines: 3
  }
);

test({
  a: {
    b: 10
  },
  c: 20,
  d: 30,
  e: 40,
  f: 50,
  g: 60,
  h: {
    i: 70
  }
});

Functions

Rules:

  • Function blocks must have a space before the definition.
  • Function must have a space before the opening parenthesis.
  • Named functions must not have a space before the opening function brackets.
  • Functions can be on a single line.
    • If they are there must be a whitespace inside the curly brackets.
  • Anonymous functions need to have a space before the opening function bracket.
  • Arrow functions
    • can be on a single line.
    • must omit the parameter brackets if only one parameter is present.
    • must omit curly brackets if only one statement is given.
    • must have whitespace around the parameter definition

Examples:

function test() {
  return;
}

function test() { var a = 10; return a; }

var test = function () { var b = 10; return b; };

var es6 = parameter => parameter();

var es6 = parameter => {
  parameter();
  return false;
};

var es6 = (parameter, index) => parameter(index);

var es6 = (parameter, index) => {
  parameter(index);
  return false;
};

Control Statements

Rules:

  • Space after the keyword
  • Space before opening parentheses
  • Strict equal (=== or !==)
    • exception to this rule is null checking

Examples:

if (a === b) {
  a();
}

if (true !== false) {
  // Statements
}

if (a == null) {
  // Statements
} else {
  // Statements
}

if (true !== false) {
  // Statements
} else if(false === true) {
  // Statements
} else {
  // Statements
}

switch (a) {
  case 1:
    break;
  case 2:
    break;
  default:
    break;
}

for (var a = 10; a !== 0; a--) {
  // Statements
}

JSDoc

JSDoc blocks should be avoided in favor to code descriptiveness. If they are necessary these rules apply:

  • If there is a return there must be a type and description.
  • If there is one or multiple parameter/s there must be a name, type and description for each one.

Example:

/**
 * Description how the function behaves.
 *
 * @param {Function} a A function containing a callback.
 */
function b(a) {
  a();
}

/**
 * Description how the function behaves.
 *
 * @param {Function} a A function containing a callback.
 * @return {String} Returns a String containing "done".
 */
function test(a) {
  a();
  return "done";
}

/**
 * Description how the function behaves.
 *
 * @param {Number} a A Number on how often the b should be called.
 * @param {Function} callback A function containing a callback function.
 * @return {String} Returns a String containing "done".
 */
function test(number, callback) {
  var counter;
  for (counter = 0; counter <= number; counter++) {
    callback();
  }
  return "done";
}

Ternaries

Rules:

  • We are using ternaries only for single line values.
    • Operators are placed at the beginning of the line.
    • Use ternaries sparingly.
var title = !Util.isStringAndEmpty(props.title)
  ? <h3 className="h3">{props.title}</h3>
  : null;

JSX

Self Contained Elements

On self contained element attributes must be indented with 2 spaces.

Example:

<PromptDialogComponent data={dialogData}
  onAccept={this.handleAcceptDialog}
  onDismiss={this.handleDismissDialog} />

Non Self Contained Elements

On elements which are not self contained the indentation of attributes must be 4 spaces. And the childNodes must have a indentation of 2 spaces to the element and -2 spaces to the attributes.

Example:

<PromptDialogComponent data={dialogData}
    onAccept={this.handleAcceptDialog}
    onDismiss={this.handleDismissDialog}>
  <ChildNode />
</PromptDialogComponent>