Value disappears after click event [duplicate]

问题

This question already has answers here:

Can I make a <button> not submit a form? (8 answers)

Closed 4 years ago.

I try to make a calculator with javascript with the onclick event I want the value of the button to convert an input text box. When I write the code the value of the button briefly in the text box , but it disappears instantly.

The code that i use can you find below this text, what am i doing wrong.
HTML:

    var iGetal = 0;
    function GetalRekenmachine()
    {
        iGetal = iGetal + 1;
        document.getElementById("Display").value = iGetal;
    }

 <button id="Cijfer7" value="7" onclick="GetalRekenmachine()">7</button>
    <input type="text" id="Display"/>
    


    

回答1:

Because the default type of a button is submit. So either cancel the click action or set the type to be button.

<button id="Cijfer7" value="7" onclick="GetalRekenmachine(); return false;">7</button>

or

<button type="button" id="Cijfer7" value="7" onclick="GetalRekenmachine()">7</button>

回答2:

var iGetal = 0;
    function GetalRekenmachine(event)
    {
        iGetal = iGetal + 1;
        document.getElementById("Display").value = iGetal;
        event.preventDefault()
    }

<button id="Cijfer7" value="7" onclick="GetalRekenmachine()">7</button>
    <input type="text" id="Display"/>

来源：https://stackoverflow.com/questions/35988724/value-disappears-after-click-event