使用jQuery以编程方式“勾选”复选框

Question

I want to trigger a programmatically checked checkbox. eg:

$(function(){
    //create a trigger that if a checkbox changes, eg is clicked/change show an alert
    $("#idCheckbox").on("change", function(){
        if($(this).is(':checked')){
            alert("Is checked!");
        }
    });

    //onload put it checked
    $("#idCheckbox").attr("checked", "checked");
});

The 'problem' is that if I check on load the checkbox by javascript the on() method is not triggered, and the alert is not shown.

The code above is an example, in fact the script which check the checkbox is not mine and I can't modify it.

I am using jQuery 1.8.0

Any suggestion?

Thanks in advance.

Answer 1

Rather than setting the attribute to checked you can call click() on the checkbox to trigger the the event you had bound previously

---

$(function(){
    var $checkbox = $("#idCheckbox");
    $checkbox.on("change", function(){
        if(this.checked){
            alert("Is checked!");
        }
    });

    $checkbox.click();
});

---

example: http://jsfiddle.net/hunter/wpLb2/

Answer 2

You can move your inline defined function to global scope and call it:

function checkBoxClick(){
    if($(this).is(':checked')){
        alert("Is checked!");
    }
}

$(function(){
    //create a trigger that if a checkbox changes, eg is clicked/change show an alert
    $("#idCheckbox").on("change", checkBoxClick);

    // Trigger your click function
    checkBoxClick();    

    //onload put it checked
    $("#idCheckbox").attr("checked", "checked");


});

Answer 3

When a checkbox is checked programmatically using javascript, onchange event does not get fired automatically. So the script that marks the checkbox as checked should call onchange event.