Logical operator in a handlebars.js {{#if}} conditional

javascript

prompt-engineering

functions

callbacks

byNikita Barsukov·Jan 2, 2025

For complex conditions in Handlebars {{#if}} blocks, create a custom helper:

// Because who needs to write `if (v1 && v2)` in pure JavaScript, am I right? 😉
Handlebars.registerHelper('and', (v1, v2) => v1 && v2);

Then watch the magic happen:

{{#if (and var1 var2)}}
  <!-- Content for true condition -->
{{else}}
  <!-- Content for false condition -->
{{/if}}

This neatly integrates logical AND operations directly in your templates.

Mastering custom helpers

Bricks for logic nirvana

To grace your templates with OR and NOT operations, register these handy helpers:

// I'm the wizard behind the curtain, making your code look cleaner 🧙
Handlebars.registerHelper({
  and: (v1, v2) => v1 && v2,
  or: (v1, v2) => v1 || v2,
  not: (v1) => !v1
});

These helpers enable virtually any JavaScript expression in your {{#if}} blocks, offering an ideal combo of dynamism and readability.

Crafted for any condition

To level-up your comparison capabilities, you can create a versatile ifCond helper:

// switch on comparisons, no monsters hidden here 🐉😃
Handlebars.registerHelper('ifCond', function (v1, operator, v2, options) {
  switch (operator) {
    case '==': return (v1 == v2) ? options.fn(this) : options.inverse(this);
    case '===': return (v1 === v2) ? options.fn(this) : options.inverse(this);
    // Add other operators as needed, no limit!
  }
});

Using good ol' switch statements, you can handle various comparison operators, taking your templates' flexibility to new heights.

Safety first

Remember to escape string expressions for security reasons when dealing with user-provided data. Beware of the injection dragon 🐉!

Supersized helpers

If you need more, custom helpers can access global functions or properties, providing extended functionalities for even the most demanding apps.

Levelling up conditional logic

Cleaner code with nested helpers

Dealing with complex expressions while keeping the template neat and tidy? Nested helpers are the dream team:

{{#if (or (and A B) C)}}
  <!-- Behold the power of nested logical conditions -->
{{/if}}

Logic operations over arrays

JavaScript array methods can save your day when logic operations over lists of items are required:

// Here, array method .some() helps me sort my life and my `if` statements out.
Handlebars.registerHelper('ifAnyTrue', function (array, options) {
  return array.some(element => element) ? options.fn(this) : options.inverse(this);
});