What Are Filters?
Filters let you transform data right inside your output tags. Instead of modifying values in a scriptlet first, you can apply a function inline with the pipe character.
<p><?= name | upper ?></p>
Filters are a shorthand for calling a function on a value. They keep your templates clean and readable.
Uppercasing Text
A common use for filters is formatting strings. You can create an uppercasing filter and apply it anywhere.
<%
var filters = {
upper: function(str) {
return str.toUpperCase();
}
};
%>
<p><?= title | upper ?></p>
Define your filters as a helper object, then reference them with the pipe. It's like a built-in formatting tool.
Formatting Dates
Filters are perfect for date formatting. Instead of writing long date logic in your template, wrap it in a filter function.
<%
var filters = {
formatDate: function(date) {
var d = new Date(date);
return d.toLocaleDateString("en-US", {
year: "numeric",
month: "long",
day: "numeric"
});
}
};
%>
<p>Published: <?= publishDate | formatDate ?></p>
Your template stays focused on structure while the filter handles the formatting logic.
Piping Multiple Transforms
You can chain multiple filters together to apply several transformations in sequence.
<%
var filters = {
upper: function(str) { return str.toUpperCase(); },
truncate: function(str) {
return str.length > 20 ? str.substring(0, 20) + "..." : str;
},
escapeHtml: function(str) {
return str.replace(/&/g, "&").replace(/</g, "<");
}
};
%>
<p><?= longText | truncate | upper ?></p>
Each filter processes the output of the previous one. This keeps complex transformations organized and reusable.