How to add an onchange event to a select box via javascript?

Add

transport_select.setAttribute("onchange", function(){toggleSelect(transport_select_id);});

setAttribute

or try replacing onChange with onchange

yourSelect.setAttribute( "onchange", "yourFunction()" );

replace:

transport_select.onChange = function(){toggleSelect(transport_select_id);};

with:

transport_select.onchange = function(){toggleSelect(transport_select_id);};

on'C'hange >> on'c'hange

You can use addEventListener too.

Here's another way of attaching the event based on W3C DOM Level 2 Events Specification:

  transport_select.addEventListener(
     'change',
     function() { toggleSelect(this.id); },
     false
  );

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