calling function with arguments in mustache javascript

Check out the section on Lambdas at https://mustache.github.io/mustache.5.html

Mustache template block:

{{#someFunction}}someValue{{/someFunction}}

Function block:

someFunction : function () {
  return function(val, render) {
    return "I passed in this value: " + render(val);
  };
}

Output:

I passed in this value: someValue