"TypeError: jQuery.easing[this.easing] is not a function" in jQuery 1.9.1

Question

For the first time in too many months (blush), I upgraded my jQuery stuff. I'm now on:

• jquery-1.9.1.js
• jquery-ui-1.10.2.custom.js (used ThemeRoller, and included all components, including the Effects Core, which mentions easing in its description)

I also upgraded to the most recent versions of jquery.multiselect and jquery.multiselect.filter plugins. When I try to close one of the multiselect menus, I get this error:

TypeError: jQuery.easing[this.easing] is not a function
jquery-1.9.1.js (line 9033)

Note that although I'm using the multiselect plugin when the error occurs, the actual error is in the main jQuery file. The code is:

/*9031*/ if ( this.options.duration ) {
/*9032*/   this.pos = eased = jQuery.easing[ this.easing ](
/*9033*/     percent, this.options.duration * percent, 0, 1, this.options.duration
/*9034*/   );
/*9035*/ }

Did I forget to update some file? Googling about it, others with the same complaint seem to all be trying to use some sort of additional easing plugin, but I'm not.

Answer 1

The error can be provoked by argument inversion when using an effect method wrongly like .show(duration, easing) as it leads to a call of an invalid easing.

The correct notation is .show(easing, duration) https://api.jquery.com/show/

var duration = 'slow', easing = 'linear';
$("#correct").click(function() {
  $("p").show(duration, easing);
});
$("#error").click(function() {
  $("p").show(easing, duration); // fails -> see error in console
});

p { background: yellow; }

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
$("p").show(
<button id="correct">duration, easing</button>
<button id="error">easing, duration -> ERROR</button>
)
<p style="display: none">Hello</p>