Conditionals

Conditionals are used to execute code based on a condition. There are 3 common ways to do this in Javascript.

• if
• if else
• switch
• ternary

I avoid using switch because it's syntax is different enough that I often forget about it's spacing or the default keyword. I prefer to use if and rarely ternary instead.

Book Source: Javascript: The Good Parts
Web Source: Doug Crockford's Javascript Code Conventions

if

This is a common way to execute code when a condition is true.

var i = 0;
if (i < 10) {
  gs.print(i);
}

if else

I generally avoid using else if possible and instead exit the code early and often. This is called guard clauses.

What does this look like? Lets consider an example where we want to only allow users with the itil role to run a script.

// this is using if else
var user = gs.getUser();
if (user.hasRole('itil')) {
  // do something
} else {
  gs.print('You do not have permission to run this script');
}

// this is using guard clauses
var user = gs.getUser();
if (!user.hasRole('itil')) {
  gs.print('You do not have permission to run this script');
  return;
}
// do something

The reason I prefer guard clauses is because it's easier to read and understand. It's also easier to test. I can test the guard clause and the if statement separately. I can't test the if statement without the else statement.

ternary

This is a common way to execute code when a condition is true or false.

var i = 0;
var result = i < 10 ? 'less than 10' : 'greater than 10';
gs.print(result);

It's important to understand how this works and for me that's seeing the same function converted to an if statement.

var i = 0;
if(i < 10) {
  gs.print('less than 10');
} else {
  gs.print('greater than 10');
}