Question

Why this works

    document.getElementById("myCheckbox").checked = false;

whereas this doesn’t with jquery:

    $("myCheckbox").attr("checked") = false;

Answer 1

There are a couple of things wrong with your code. First of all, you select elements in jQuery using selectors, just like in CSS. So you need to turn this

$("myCheckbox")

into this, using the hash (#) for ID selector

$("#myCheckbox")

Secondly, jQuery doesn’t really use properties, but methods for everything. Pass one parameter to get a value, two to set it. In this case, you also want to be using prop and not attr. So you would need to do:

$("#myCheckbox").prop("checked", false);

Live example