Table of Contents

JavaScript coding guidelines
- General
- Naming conventions
- Variables
- Conditional statements
- Loops
  - For
  - While
  - Do/While
  - forEach() iterator
- Formatting
- Comparison
- General structure

JavaScript coding guidelines

General

Using global variables (e.g. global = 1) should be avoided as much as possible.

Naming conventions

All names must be written in English.
Variables must be written in lowercase characters separated by underscores.

Good example:

var hostid = 12345,
           item_applications = [];

Bad example:

var Hostid = 12345,
           itemApplications = [];

Prefix variable names with $ only when they contain jQuery objects.

Good example:

var $widget_header = $('.widget_header', $widget),
           host_count = 5;

Bad example:

var widget = $('.widget_container'),
           $hosts = [$('#host1'), $('#host2')];

Function names (except constructors) must use lower camel case.

Good example:

function create() {
           // some logic here
       }
       
       function getName() {
           // some logic here
       }

Bad example:

function Create() {
           // some logic here
       }
       
       function get_name() {
           // some logic here
       }

Variables

Variable declaration

Each variable must be declared on a separate line.
Multiple variables must be separated by a comma.

Good example:

var itemids = [],
           item_applications = [];

Bad example:

var itemids = [];
       var item_applications = [];

Bad example:

var itemids = hostids = [];
       
       var left = null, top = null, right = null, bottom = null;
       
       var itemIds = [],
           itemApplications = [];

Objects

Do not use quotes when creating object entities.

Good example:

var person = {firstname: 'Mario', lastname: 'Smith'};
       
       person.firstname = 'Mr.';

Bad example:

var person = {"firstname": 'Mario', "lastname": 'Smith'};

Assignments

Avoid multiple left-hand assignments on a single line.

Good example:

curr_lbl.style.background = background;
       curr_lbl.style.color = background;

Bad example:

curr_lbl.style.background = curr_lbl.style.color = background;

Wrap complex statements assigned to a variable in parentheses.

Good example:

var disable = (return_code === '-1' && service_enabled);

Bad example:

var disable = return_code === '-1' && service_enabled;

Conditional statements

The opening brace is written on the same line as the conditional statement.
The closing brace is always written on its own line.

Good example:

if (list.length > 100) {
           // some logic here
       }

Bad example:

if (list.length > 100)
       {
           // some logic here
       }

If/Else/Else if

"If" statements must always use curly braces {}.

Good example:

if (list.length > 100) {
           // some logic here
       }
       
       if (list.length > 100) {
           // some logic here
       } else {
           // some logic here
       }
       
       if (list.length > 100) {
           // some logic here
       } else if (list.length == 1) {
           // some logic here
       } else {
           // some logic here
       }

Bad example:

if (list.length > 100) // some logic here
       
       if (list.length > 100) {
           // some logic here
       } else {
           // some logic here
       }

Use "else" or "else if" when possible, avoiding separate "if" statements.

Good example:

if (a == b) {
           d = e;
       }
       else if (a == c) {
           d = f;
       }
       else {
           d = g;
       }

Bad example:

if (a == b) {
           d = e;
       }
       if (a == c) {
           d = f;
       }
       if (a != b && a != c) {
           d = g;
       }

Switch

If we fall through, the comment should be present, confirming that it's intentional.

Example:

switch (condition) {
           case 1:
               // some logic here
               // falls through
           case 2:
               // some logic here
       break;
       
           case 3:
               // some logic here
       break;
       
           default:
               // some logic here
       break;
       }

Try/Catch

Example:

try {
           // some logic here
       } catch (exception if condition) {
           // some logic here
       } finally {
           // some logic here
       }

Loops

For

Example:

for (var i = 0; i < list.length; i++) {
           // some logic here
       }

While

Example:

while (list.length > 0) {
           // some logic here
       }

Do/While

Example:

do {
           // some logic here
       } while (list.length > 0);

forEach() iterator

Example:

['<some_array>'].forEach(function (field) {
           // some logic here 
       });

Formatting

Limit lines to 200 characters.

Strings

Use single quotes for strings when possible.
Add spaces around + in string concatenations.

Good example:

const x = 'string';

Bad example:

const x = "string";

Blank spaces

Use a single space after commas in argument lists.

Good example:

function updateUserProfile(idx, value_int, idx2) {
           // some logic here
       }

Bad example:

function updateUserProfile(idx,value_int,idx2) {
           // some logic here
       }

Use spaces around binary operators, but do not add spaces between unary operators (like -, ++, --) and their operands.
Use a space between a keyword and the following parenthesis.

Good example:

if (n !== 0 && n !== (1 / 0) && n !== -(1 / 0)) {
           n = (n > 0 || -1) * Math.floor(Math.abs(n));
       }

Bad example:

if(n!==0&&n!==(1/0)&&n!==-(1/0)){
           n=(n>0||-1)*Math.floor(Math.abs(n));
       }

Use a space after a colon before a keyword.

Good example:

init: function(time) {
           this.delay = time;
           this.delayLeft = this.delay;
           this.start();
       }

Bad example:

init:function(time) {
           this.delay = time;
           this.delayLeft = this.delay;
           this.start();
       }

Blank lines

Use a blank line after variable declarations, around statements, and before return.

Good example:

var footerButton = GetData(e.target),
           form = footerButton.closest('form'),
           confirmText = footerButton.attr('confirm');
       
       if (confirmText && !confirm(confirmText)) {
           Event.stop(e);
       
           return false;
       }

Bad example:

var footerButton = GetData(e.target),
           form = footerButton.closest('form'),
           confirmText = footerButton.attr('confirm');
       if (confirmText && !confirm(confirmText)) {
           Event.stop(e);
           return false;
       }

Comments

Use only // double slashes for comments.

Example:

// simple comment

Start block comments with a capital letter.

Example:

//
       // New block comment.
       //

Use full words in comments (e.g., parameter instead of param).
Write multiline comments using block syntax and keep within the maximum line length.
Omit comments if the code is self-explanatory.

Comparison

Use == equal or != not equal operators when comparing numeric values to zero.

Good example:

if (itemid != 0) {}

Bad example:

if (itemid) {}

Use typeof to check if a variable is undefined.

Good example:

if (typeof variable !== 'undefined') {}

Bad example:

if (variable !== undefined) {}

General structure

Decouple logic from the main function by placing it in a separate object.
Keep the main function simple and avoid unnecessary complexity.
Exception: simple functions may remain self-contained.

Good example:

var SinteticData = {
           params: {
               min: 0,
               // some params
           },
       
           setParams: function (params) {
               // some magic here
           },
       
           getSin: function (min, max, shift, period) {
               // some magic here
           },
       
           getValue: function () {
               // some magic with call getSin()
           }
       }
       
       try {
           SinteticData.setParams(JSON.parse(value));
       
           return SinteticData.getValue();
       } catch (error) {
           error += (String(error).endsWith('.')) ? '' : '.';
       
           Zabbix.log(3, '[ DEMO ] ERROR: ' + error);
       
           return JSON.stringify({ 'error': error });
       }

Bad example:

var SinteticData = {
           params: {
               min: 0,
               // some params
           },
       
           setParams: function (params) {
               // some magic here
           },
       
           getSin: function (min, max, shift, period) {
               // some magic here
           }
       }
       
       try {
           SinteticData.setParams(JSON.parse(value));
       
           var tmp_data = SinteticData.getSin(SinteticData.params),
               tmp_data2 = [],
               tmp_out = '';
       
           for (var i = 0; i < tmp_data.length; i++) {
               // some magic with update tmp_data2
           }
       
           for (var j = 0; j < tmp_data.length; j++) {
               // some magic with update tmp_out
           }
       
           return tmp_out;
       } catch (error) {
           error += (String(error).endsWith('.')) ? '' : '.';
       
           Zabbix.log(3, '[ DEMO ] ERROR: ' + error);
       
           return JSON.stringify({ 'error': error });
       }

Treat all external data structures (objects, arrays, input parameters) as unreliable and validate them before use.

For example, check the input parameters:

...
           setParams: function (params) {
              ['min', 'max', 'shift', 'mutation_t', 'mutation_v', 'mutation_r', 'period'].forEach(function (field) {
                  if (typeof params === 'object' && typeof params[field] !== 'undefined' && params[field] !== '') {
                      SinteticData.params[field] = parseFloat(params[field]);
                  }
              });
          }
       ...

Avoid directly accessing object properties by key or array element by index; use dedicated methods instead.

Good example:

var data = some_object.getField('property');

Bad example:

var data = some_object['property'];

Always catch exceptions and provide complete information about their cause.

Good example:

try {
           credentials = JSON.parse(credentials);
       } catch (error) {
           throw 'Failed to parse response received from instance metadata. Check debug log for more information.';
       }

Bad example:

credentials = JSON.parse(credentials);

Avoid copying blocks of code; consider using file inclusion instead.

Example:

params:
           include:
           - ./scripts/oci_validate_zbx_params.js
           - ./scripts/oci.js
           - ./scripts/compute/oci_compute_health_metrics_POST.js

For HTTP requests, provide proxy support.

Example:

if (typeof AWS.params.proxy !== 'undefined' && AWS.params.proxy !== '') {
           request.setProxy(AWS.params.proxy);
       }

For logging, use tags to identify the process.

Good example:

Zabbix.log(3, '[ AWS Billing ] ERROR: ' + error);

Bad example:

Zabbix.log(3, error);

Documentation

JavaScript coding guidelines

General

Naming conventions

Variables

Variable declaration

Objects

Assignments

Conditional statements

If/Else/Else if

Switch

Try/Catch

Loops

For

While

Do/While

forEach() iterator

Formatting

Strings

Blank spaces

Blank lines

Comments

Comparison

General structure