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Asked: 2026-05-31T23:13:19+00:00

I have an image that I want to move. I can move the element

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I have an image that I want to move. I can move the element with javascript if I have the HTML below:

<html>
<head>
    <title>Snake</title>
    <script type="text/javascript" src="snake.js"></script>
    <!-- <link type="text/css" href="snake.css"> -->
</head>
<body onKeyPress="ProcessKeypress(event);">
    <p><img id="snake" style="z-index: 0; left: 300px; position: absolute; top: 250px" 
    float=top border=0 hspace=0 src="snake.gif"></p>
</body>

However I want to stye the image element using CSS. When I do this my code to move the image does not work. HTML and CSS below are what I would like to use.

<html>
<head>
    <title>Snake</title>
    <script type="text/javascript" src="snake.js"></script>
    <link type="text/css" href="snake.css">
</head>
<body onKeyPress="ProcessKeypress(event);">
    <p><img id="snake" src="snake.gif"></p>
</body>


@CHARSET "UTF-8";
img {
z-index: 0;
left: 300px; 
position: absolute; 
top: 250px;
float: top;
border: 0;
hspace: 0;
}

JavaScript below is what I am using to move the image. Any and all help appreciated. 

function moveObj(name, Xpix, Ypix) 
{    
    obj = document.getElementById(name);

    px = parseInt(obj.style.left) + Xpix;       
    py = parseInt(obj.style.top) + Ypix;
    obj.style.left = px;
    obj.style.top = py;
}

function ProcessKeypress(e)
{
    var myObj = 'snake';
    var moveBy = 10;

    if(e.keyCode === 97) {
        moveObj(myObj, -moveBy, 0);
    }
    else if(e.keyCode === 100) {
        moveObj(myObj, moveBy, 0);
    }
    else if(e.keyCode === 115) {
        moveObj(myObj, 0, moveBy);
    }
    else if(e.keyCode === 119) {
        moveObj(myObj, 0, -moveBy);
    }
}
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1 Answer

  1. Editorial Team

    obj.style.left accesses the style properties defined in inline only.

    UPDATE

    Here is your pure JavaScript Solution

    Function: getStyleProp() to get the current applied style [Source]

    function getStyleProp(elem, prop){
    if(window.getComputedStyle)
        return window.getComputedStyle(elem, null).getPropertyValue(prop);
    else if(elem.currentStyle) return elem.currentStyle[prop]; //IE
}

    Function: moveObj()

    function moveObj(obj, Xpix, Ypix) {  
    obj.style.left = parseInt(getStyleProp(obj,'left')) + Xpix+"px";
    obj.style.top= parseInt(getStyleProp(obj,'top')) + Ypix + "px";
}

    Function: ProcessKeypress()

    function ProcessKeypress(e) {
    var myObj = document.getElementById("snake");
    var moveBy = 10;
    switch(e.charCode) {
        case 97: moveObj(myObj, -moveBy, 0); break;
        case 100: moveObj(myObj, moveBy, 0); break;
        case 115: moveObj(myObj, 0, moveBy); break;
        case 119: moveObj(myObj, 0, -moveBy); break;            
    }
}

    I also solved your case using jQuery: Demo

    Function moveObj

    function moveObj(obj, Xpix, Ypix) {    
    obj.css('left', parseInt(obj.css('left')) + Xpix);       
    obj.css('top', parseInt(obj.css('top')) + Ypix);
}

    Function ProcessKeypress

    function ProcessKeypress(e) {
    var myObj = $("#snake"); //It will be better if it is cached
    var moveBy = 10;
    switch(e.charCode) { //used Switch for better manageability
        case 97: moveObj(myObj, -moveBy, 0); break;
        case 100: moveObj(myObj, moveBy, 0); break;
        case 115: moveObj(myObj, 0, moveBy); break;
        case 119: moveObj(myObj, 0, -moveBy); break;            
    }
}

    Event Trigger attached to document instead

    $(document).on('keypress', ProcessKeypress);
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