javascript - Why are jQuery objects in property initialization empty? -

'use strict'; var controller = function controller() {};  controller.init = function() {   if (!controller.propertie.element || !controller.propertie.indicator) {     return 'expected find [data-controller] , [data-controller-to]';   }    controller._start(); };  controller.propertie = {   element: $('[data-controller]'),   indicator: $('[data-controller-to]'),   state: false };  controller._start = function() {   controller.propertie.indicator.bind('click', controller._toggle); };  controller._toggle = function() {   controller.propertie.element     .animate({       bottom: (controller.propertie.state = !controller.propertie.state) ? '-110' : '0'     }); }; 

apparently elements in object property not exist, exist ! tell me if can not use javascript that?

maybe there hoisting breaking script?

i try put object before init , result same.

i know can extend prototype, have reasons use this.

thanks.

i can think of 3 possible causes:

1. the code being initialized before dom has been parsed.
2. your html not contain elements match these selectors.
3. the desired elements being created dynamically after code being initialized.

in declaration:

controller.propertie = {   element: $('[data-controller]'),   indicator: $('[data-controller-to]'),   state: false }; 

the 2 jquery expressions evaluated code parsed. if code not placed @ end of body, elements not exist yet.

the usual solution not initialize elements in static declaration, initialize them calling function after page has been loaded.

if intend them globals, this:

$(document).ready(function() {     controller.propertie = {       element: $('[data-controller]'),       indicator: $('[data-controller-to]'),       state: false     }; }); 

but, have make sure don't try use them until after code runs.

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the other possible cause can think of dom not contain elements match 2 selectors. seems it's 1 of these 2 issues. since haven't shown either overall page structure of html intend match, it's impossible other tell causes might be.