how does jquery fadeIn work? Doing the same with animate()

Question

I love the simple jQuery fadeIn() function, especially because it works without having to set any opacity values to the selector! Just setting it to display:none and using fadeIn() always works.

However I'm not using jQuery for my current project but zepto.js. Zepto only comes with animate() and not with fadeIn().

I wonder how I can create the same behaviour with the animate function! What properties do I have to animate here?

$('#selector').animate({
    display: "block",
    opacity: 1
}, 500, 'ease-out')

Thank you in advance

Answer 1

(function($){
      $.extend($.fn, {
        fadeIn: function(ms){
          if(typeof(ms) === 'undefined'){
            ms = 250;
          }
          $(this).css({
            display: 'block',
            opacity:0
          }).animate({
            opacity: 1
          }, ms);
          return this;
        }
      })
    })(Zepto)

If Zepto works like jQuery $('.example').fadeIn(); should do the trick.

EDIT: Trejder is right, adjusted the parts.

Answer 2

The jQuery fadeIn function is just a shortcut to the jQuery animate function. All it does it change the opacity from 0 to 1 over a period of time by incrementing the opacity value.

// Generate shortcuts for custom animations
jQuery.each({
    slideDown: genFx( "show", 1 ),
    slideUp: genFx( "hide", 1 ),
    slideToggle: genFx( "toggle", 1 ),
    fadeIn: { opacity: "show" },
    fadeOut: { opacity: "hide" },
    fadeToggle: { opacity: "toggle" }
}, function( name, props ) {
    jQuery.fn[ name ] = function( speed, easing, callback ) {
        return this.animate( props, speed, easing, callback );
    };
});