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Eleventy Documentation

Custom Tags

It’s unlikely that you want this feature. You probably want shortcodes instead, Eleventy’s custom tags sugar (it’s easier to use).

Various template engines can be extended with custom tags.

Custom Tags are unrelated to Eleventy’s Collections using Tags feature. Unfortunately we’ve inherited this name from various upstream template languages.

But, after all that, you can still add a Custom Tag using the Configuration API.

LiquidJS example

Filename .eleventy.js
module.exports = function(eleventyConfig) {
  // Usage: {% uppercase myVar %} where myVar has a value of "alice"
  // Usage: {% uppercase "alice" %}
  eleventyConfig.addLiquidTag("uppercase", function(liquidEngine) {
    return {
      parse: function(tagToken, remainingTokens) {
        this.str = tagToken.args; // myVar or "alice"
      },
      render: function(scope, hash) {
        // Resolve variables
        var str = liquidEngine.evalValue(this.str, scope); // "alice"

        // Do the uppercasing
        return Promise.resolve(str.toUpperCase()); // "ALICE"
      }
    };
  });
};

See all of the built-in tag implementations for LiquidJS.

Nunjucks example New in v0.5.0

Filename .eleventy.js
module.exports = function(eleventyConfig) {
  // Usage: {% uppercase myVar %} where myVar has a value of "alice"
  // Usage: {% uppercase "alice" %}
  eleventyConfig.addNunjucksTag("uppercase", function(nunjucksEngine) {
    return new function() {
      this.tags = ["uppercase"];

      this.parse = function(parser, nodes, lexer) {
        var tok = parser.nextToken();

        var args = parser.parseSignature(null, true);
        parser.advanceAfterBlockEnd(tok.value);

        return new nodes.CallExtensionAsync(this, "run", args);
      };

      this.run = function(context, myStringArg, callback) {
        let ret = new nunjucksEngine.runtime.SafeString(
          myStringArg.toUpperCase()
        );
        callback(null, ret);
      };
    }();
  });
};

Handlebars example

Surprise—these are helpers!

Filename .eleventy.js
module.exports = function(eleventyConfig) {
  // Usage: {{ uppercase myVar }} where myVar has a value of "alice"
  // Usage: {{ uppercase "alice" }}
  eleventyConfig.addHandlebarsHelper("uppercase", function(myStringArg) {
    return myStringArg.toUpperCase();
  });
};

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