undefined is not a function while adding event handlers

Question

I am trying to get a list of buttons and add event listeners for each of it on domloaded

     window.addEventListener('DOMContentLoaded', function() {  
        var calKeys = document.getElementById("filters").querySelectorAll("a.Button");
        registerKeys(calKeys);
        var registerKeys = function(inputs){
             for(var i=0;i<inputs.length;i++) {
                    inputs[i].addEventListener("click", handleCalcKey, false);
            }
        };
        var handleCalcKey = function(){
             alert( "thi sis a test");
        }
     });

So my registerKeys method basically takes teh inputs and adds the handler. however it fails as uncaught type error undefined is not a function

Not sure what is going on....

You know the console (F12) points the exact location of the error ? — Denys Séguret
– Denys Séguret, Commented Jul 28, 2014 at 20:13
a.Button is anchors with HTML class='Button'. Just seeing if you knew that. Also, code is not backward compatible. — StackSlave
– StackSlave, Commented Jul 28, 2014 at 20:15

Denys Séguret · Accepted Answer · 2014-07-28 20:13:52Z

4

There :

registerKeys(calKeys);
var registerKeys = function(inputs){

you call a function one line before you define it. The variable declaration is hoisted, not the assignation.

You could do it like this :

registerKeys(calKeys);
function registerKeys(inputs){

but it's generally not very readable. Unless there's a good reason (there doesn't seem to be one here), it's clearer when values are given before they're used.

answered Jul 28, 2014 at 20:13

Denys Séguret

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