javascript - Why is my JS function executed onload instead of onchange? - Stack Overflow

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Here's the code:

window.onload = function() {
    oldonload && oldonload();

    function test() {
        alert("meh");
    }    

    $('input[type=file]').change(test());
}

The code is fairly straight forward, test() is called only when input[type=file] is changed. However test() is being called whenever my page is loaded.

What is going on here? How would I execute the function only when user interacts with the input element?

Here's the code:

window.onload = function() {
    oldonload && oldonload();

    function test() {
        alert("meh");
    }    

    $('input[type=file]').change(test());
}

The code is fairly straight forward, test() is called only when input[type=file] is changed. However test() is being called whenever my page is loaded.

What is going on here? How would I execute the function only when user interacts with the input element?

• javascript
• jquery
• input
• jquery-events

Share Improve this question Follow edited Aug 21, 2020 at 12:33 Brian Tompsett - 汤莱恩 5,8937272 gold badges6161 silver badges133133 bronze badges asked May 11, 2016 at 6:11 Joel MinJoel Min 3,45733 gold badges2222 silver badges3838 bronze badges 1

• It happens on load, because you said it so, use onclick. – Bálint Commented May 11, 2016 at 6:13

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4 Answers 4

Sorted by: Reset to default 7

You are calling the method on this line:

$('input[type=file]').change(test());

Change it to:

$('input[type=file]').change(test);

If you want to pass a parameter to test:

var myVar = 5;
$('input[type=file]').change(function () {
   test(myVar); 
});

Just change the file change event like this :

 $('input[type=file]').change(function() { test() });

You're executing the function immedietaly instead of assigning a handler. You should instead do:

$('input[type=file]').change(test);

change takes function as argument, so you just need to provide function name to be called.

$('input[type=file]').change(test);

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