Question

I check the jQuery plugin site, which teach me how to write a basic plugin:

(function( $ ){
  $.fn.maxHeight = function() {
    var max = 0;
    this.each(function() {
      max = Math.max( max, $(this).height() );
    });
    return max;
  };
})( jQuery );

Then, the div can have the maxHeight method, like this:

var tallest = $('div').maxHeight(); // Returns the height of the tallest div

But I would like to only textarea have maxHeight function, but not the div. How can I do so?

Answer 1

Check to make sure the element is a textarea before checking/saving the height.

this.each(function() {
    if(this.tagName.toLowerCase() === "textarea") {
        max = Math.max( max, $(this).height() );
    }
});

jQuery plugins don’t give functions to certain elements, they give functions to the jQuery object for working with a set of selected elements. The best solution would be to keep them as generic as possible and only call $("textarea").maxHeight() when you need it. You aren’t doing anything specific to textareas in the plugin and if you leave it as it is now, you don’t need to make a change to it in the future if $('div').maxHeight() becomes a required use-case.