Specific examples of JS random floating advertising code_javascript skills

<script>
var x = 50, y = 60 //The initial position of the floating layer corresponds to the initial X coordinate and Y coordinate of the layer respectively
var xin = true, yin = true //Determine whether the X coordinate and Y coordinate of the layer are within the control range. If xin is true, the layer moves to the right, otherwise to the left; if yin is true, the layer moves downward, otherwise upward
var step = 1 //Layer The step length of movement. The larger the value, the faster the movement speed.
var delay = 10 //The time interval for layer movement, in milliseconds. The smaller the value, the faster the movement speed.
var obj=document.getElementByIdx_x("float ") //Capture the layer with id ad as a floating target
function floatAD() {
var L=T=0 //The left boundary (L) and upper boundary (T) coordinates of the layer movement range
var R= document.body.clientWidth-obj.offsetWidth //The right boundary of the layer movement
var B = document.body.clientHeight-obj.offsetHeight //The lower boundary of the layer movement
obj.style.left = x document.body.scrollLeft //Update the X coordinate of the layer to realize movement in the Within the visible range
obj.style.top = y document.body.scrollTop //Update the Y coordinate of the layer to achieve movement in the Y-axis direction; document.body.scrollTop is the downward distance of the scroll bar in the document area , to ensure that the layer is still within the visible range when the scroll bar is pulled down
x = x step*(xin?1:-1) //Determine the movement direction of the layer on the X axis by judging the range of the layer
if (x < L) { xin = true; x = L} //Handling when the layer exceeds the left boundary
if (x > R){ xin = false; x = R} //When the layer exceeds the right boundary Processing
y = y step*(yin?1:-1) //Determine the movement direction of the layer on the Y axis by judging the range of the layer
if (y < T) { yin = true; y = T } //Handling when the layer exceeds the upper boundary
if (y > B) { yin = false; y = B } //Handling when the layer exceeds the lower boundary
}
var itl= setInterval("floatAD()", delay) //Execute the floatAD function every delay seconds
obj.onmouseover=function(){clearInterval(itl)} //The layer clears the above interval event when the mouse moves up, to achieve The effect of stopping the movement of the layer when the mouse moves up
obj.onmouseout=function(){itl=setInterval("floatAD()", delay)} //The layer starts interval events when the mouse moves away to realize the layer's movement when the mouse moves up The effect of continuing to move when the mouse is removed
</script>