how to change background image dynamically only wh

问题:

how to change background image dynamically only when radio button is selected and by pressing submit button

link to sample

回答1:

Using only Javascript

Test it online: http://jsfiddle.net/OscarGarcia/t70prkda/

HTML test code:

<form name="form" onsubmit="return check()">
    <p><input type="radio" name="bg" value="no" />
        Desactivate</p>
    <p><input type="radio" name="bg" checked="checked" value="yes" />
        Activate</p>
    <input type="submit" />
</form>

Javascript code:

function check() {
    if (document.form.bg.value == "yes") {
        document.body.style.background = "red";
    } else {
        document.body.style.background = "";
    }
    return false;
}

Edit 1: Using jQuery

Test it online: http://jsfiddle.net/OscarGarcia/t70prkda/1/

function check() {
    if ($("#form input[name=bg]:checked").val() == "yes") {
        $('body').css('background', "red");
    } else {
        $('body').css('background', "");
    }
    return false;
}

Edit 3: Changing background image in JS and jQuery

For simplicity my code only change background color, this one changes background image: http://jsfiddle.net/OscarGarcia/t70prkda/2/

function check() {
    if ($("#form input[name=bg]:checked").val() == "yes") {
        $('body').css('background-image', "url(https://c2.staticflickr.com/8/7151/6717697085_6d28849226_z.jpg)");
    } else {
        $('body').css('background', "");
    }
    return false;
}

And in pure javascript: http://jsfiddle.net/OscarGarcia/t70prkda/3/

function check() {
    if (document.form.bg.value == "yes") {
        document.body.style.backgroundImage = "url(https://c2.staticflickr.com/8/7151/6717697085_6d28849226_z.jpg)";
    } else {
        document.body.style.background = "";
    }
    return false;
}

Edit 3: Smooth background image transition

Try it online: http://jsfiddle.net/OscarGarcia/2g6rfdsf/

CSS Code:

body {
    height: 100%;
}

#overlay {
    position: absolute;
    top: 0px;
    left: 0px;
    padding: 0px;
    margin:0px;
    width: 100%;
    height: 100%;
    background: red url(http://thumbs.dreamstime.com/z/abstract-blue-tiled-background-5151518.jpg) -400px center;
    transition: all 2s ease-in-out;
    opacity: 0;
    z-index: -1;
}

HTML Code:

<div id="overlay"></div>
<form name="form" id="form" onsubmit="return check()">
    <p><input type="radio" name="bg" value="no" />
        Fade-out</p>
    <p><input type="radio" name="bg" checked="checked" value="yes" />
        Fade-in</p>
    <input type="submit" />
</form>

Note that I'm using an overlay (a div over the background) with opacity 0 (hidden) and I'll animate the opacity. It's not possible to animate background image changes, they will change instantly.

And javascript (jQuery version) code:

function check() {
    if ($("#form input[name=bg]:checked").val() == "yes") {
        $('#overlay').
            css('opacity', '1').
            css('background-position', '0px center');
    } else {
        $('#overlay').
            css('opacity', '0').
            css('background-position', '-400px center');
    }
    return false;
}

When pushing button background overlay will show or hidden smoothly because CSS code transition: all 2s ease-in-out; while left position changes slowly too!.

Hope it helps!

回答2:

You will want to use jquery to register the eventHandler with both actions.

Something like:

var backgroundHandler = function(){//whatever};
$('#radioWhatever').on('changed',backgroundHandler);
$('#submitbtn').on('click', backgroundHandler);