What are filters in Vue.js?

In Vue.js, filters are functions that can be used to apply common text formatting to data before displaying it in the user interface. They are primarily used for simple text transformations, such as formatting dates, currency, and capitalization.

Here’s how filters work in Vue.js:

1. Definition: Filters are defined globally using the Vue.filter() method or locally within a specific Vue component.
2. Syntax: Filters are applied within double curly braces ({{ }}) in the template.
3. Usage: Filters can be chained together and can accept arguments.
4. Example:
   javascriptCopy code

   // Global filter definition
   Vue.filter('capitalize', function(value) {
   if (!value) return '';
   value = value.toString();
   return value.charAt(0).toUpperCase() + value.slice(1);
   });

   // Local filter definition
filters: {
capitalize: function(value) {
if (!value) return '';
value = value.toString();
return value.charAt(0).toUpperCase() + value.slice(1);
}
}


   In template:

   htmlCopy code

   <div>{{ message | capitalize }}</div>


   In this example, the capitalize filter is used to capitalize the first letter of the message variable before displaying it.

5. Built-in filters: Vue.js provides some built-in filters such as currency, uppercase, lowercase, capitalize, json, pluralize, etc.
6. Custom filters: Developers can create custom filters to meet specific formatting needs.
7. Filter Order: Filters are applied in the order they appear in the template.
8. Performance: Filters are re-evaluated whenever the relevant data changes, so it’s essential to keep them lightweight for optimal performance.

In an interview setting, it’s good to emphasize practical examples of how filters can be used to manipulate data presentation within Vue.js applications.