Operators EJS-code

EJS (Express.js) is a web application framework for Node.js. In BILLmanager EJS is implemented with the /usr/local/mgr5/etc/scripts/template_ejs.js script. For correct operation, the incoming XML-file is converted to a JSON file. 

The EJS language describes document and message templates in BILLmanager. To add or edit templates, navigate to Settings → Document templates.

Operators allow handling various scenarios to generate a printing form of a document. The system checks conditions and executes a code based on the result. 

This article describes the following operations:

• comparison operator;
• logical operator;
• the if ... else operator;
• conditional operator;
• the switch operator.

Comparison operator

This is a binary operator that takes two operands in which values are being compared. 

Logical operators

Logical operators combine multiple boolean values and provide a single boolean output.

• && (AND) — this operator will be truthy if the expressions on both sides of it are true. 
• || (OR) —  this operator will be truthy if the expression on either side of it is true. 
• ! (NOT) — this operator converts the operand to boolean type and returns an inverse value. 

A rule of logical expression in a code is represented by the keywords true and false. True is returned if a condition is true, and false is returned if a condition is false. 

if ... else operator

Syntax:

if (logical expression) {
	piece of code 1 //it will be executed if the lofical expression is true. 
} else {
	piece of code 2  //it will be executed if the lofical expression is false. 
}

The use of  else is optional:

if (logical expression) {
	piece of code 1 //it will be executed if the lofical expression is true. 
}
piece of code 2 //it will be executed in any case regardless the logical expression.

If one condition may result in several scenarios, you can use else if. The following example shows a condition to display cents in the total amount due:

if (_second_num == 1 & _first_num != 1) _string += ' cent'; //The first condition. If it is true, the described code will be applied.
	else if (_second_num > 1 && _second_num < 5) _string += ' cents'; //The second condition. The system checks that the first condition is false. 
else _string += ' cents';// It is executed if none of the conditions are true. 

Example

You can add payer information using if ... else in the standard invoice template:

<% if ((findu(payment.customer.profiletype) == 2) || (findu(payment.customer.profiletype) == 3)) { %> // If a payer is a company
	<div class="title">Customer:&nbsp;</div>
	<div class="company"><%= findu(payment.customer.name) %></div>
	<div>VAY<%= findu(payment.customer.vatnum) %>, IBAN<%= findu(payment.customer.iban) %></div> // Show VAT and IBAN in a document. 
   	<div class="line">&nbsp;</div>
   	<div><%= findu(payment.customer.postcode_legal) %>, <%= findu(payment.customer.country_legal_name) %>, 
	<%= findu(payment.customer.city_legal) %>, <%= findu(payment.customer.address_legal) %></div>
<% } else { %> // Otherwise a payer is an individual
	<div class="title">Customer:&nbsp;</div>
   	<div class="company"><%= findu(payment.customer.person) %></div>
   	<div class="line">&nbsp;</div>
   	<div><%= findu(payment.customer.postcode_physical) %>, <%= findu(payment.customer.country_physical_name) %>, 
	<%= findu(payment.customer.city_physical) %>, <%= findu(payment.customer.address_physical) %></div> // Show the customer address in a document.
<% } %>

In the code above, the system checks a payer type. If it is a company, its VAT number and IBAN will be displayed in the document. Otherwise, a customer is considered an individual, and the document will show his address. 

Conditional operation. 

A conditional operator is an alternative to if... else. Conditional operators return one value if the condition is true and returns another value if the condition is false.

Syntax:

(condition)?piece of code 1:piece of code 2

The system applies the piece of code 1  if the condition is true. If the condition is false, it applies the piece of code 2. 

Example

The following function converts a digit into a string:  

var n=!isFinite(+number)?0:+number

It can be explained as  "if the expression+number is not a finite number, the n variable is assigned 0, otherwise n is assigned +number". 

switch operator

The switch operator excepts a variable or expression and executes a required piece of code depending on the result. Its basic syntax: 

switch (expression) {
  case 1:
    piece of code 1
    break; // completed the case operator

  case 2: // there can be multiple cases (variants )
    piece of code 2
    break;
  
  default: // it is executed if the values doesn not match any result.
    piece of code 3
}

The piece of code 1 is applied if the result is 1. The piece of code 2 is applied if the result is 2, and the piece of code 3 if applied if the result is another number except for 1 and 2. 

Example

Let's describe the code that returns one of four sentences depending on the input value. This code is not used in a pre-made template in the billing system.  

switch (word) {
  case 'hi':
    phrase = 'Hello my dear friend';
    break;

  case 'bye':
    phrase = 'Goodbye, i hope to see you again';
    break;

  case 'joke':
    phrase = 'I dont know jokes';
    break;

  case 'day':
    phrase = 'Have a nice day!';
    break;

  default:
    phrase = 'I dont understand you';
}

The above code compares the values of the input variable word with possible values:

• if "word" contains the word "hi", the variable"phrase" will be assigned the value "Hello my dear friend";
• if "word" contains "bye",  the variable"phrase" will be assigned the value "Goodbye, I hope to see you again";
• if  "word" contains "joke",  the variable"phrase" will be assigned the value  "I don't know jokes";
• if "word" contains "day",  the variable"phrase" will be assigned the value  "Have a nice day";
• if the values do not match,  the variable"phrase" will be assigned the value  "I don't understand you".