CODEWITHSUNDEEP
javascript
user1087110
user1087110

Reputation: 3763

Alert message onfocus

I don't get it. Why does this alert on page load? How to make it alert only "onfocus"?

<input id="mail" name="E-post" value="E-post">
<script>
window.onload = function () {
    function onfocusFunction() {
        alert('Why!?');
    }
    var myMail = document.getElementById('mail');
    myMail.onfocus = onfocusFunction();
}
</script>

Upvotes: 0

Views: 1713

Answers (2)

Engineer
Engineer

Reputation: 48793

With parenthesis (), you are calling onfocusFunction function and assigning undefined to myMail.onfocus:

myMail.onfocus = undefined;

as your onfocusFunction function does not return anything.

Without parenthesis, you will have onfocusFunction object, which should be assigned to .onfocus:

myMail.onfocus = onfocusFunction;  //No parenthesis before ';'

UPDATE: If you want to pass parameters either, then try like this:

function onfocusFunction(param1,param2) {
    return function(){
       alert(param1+":"+param2);
    };
}
var myMail = document.getElementById('mail');
myMail.onfocus = onfocusFunction("value1","value2");

Then when onfocus event will be triggered you will see "value1:value2" as an alert.

Upvotes: 2

amd
amd

Reputation: 21472

when you type myMail.onfocus = onfocusFunction();

  1. your are calling onfocusFunction() and
  2. assigning its return value to myMail.onfocus

( in this case the return value is null );

let say : 

 function onfocusFunction() {
        alert('Why!?');
return "ok";
    }

so myMail.onfocus will be the string 'ok' instead of a function

you can use Engineer's Solution

or try :

myMail.onfocus = function(){alert("why")};

Upvotes: 0

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