Jun 12, 2020

javascript implements a light blue mouse drag selection box instance

This article shows how javascript implemented the light blue drag selection box. Share to everybody for everybody reference. Specific implementation methods are as follows:

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<style type="text/css">
#rectBox
{
background:#CCFFFF;
border:2px solid #0099FF;
filter:alpha(opacity=30);
opacity:0.3;
position:absolute;
}
</style>
<head>
<title>1 A mouse selection box </title>
<script type="text/javascript">
function Rect()
{
this.doc = document.documentElement;
if(!this.doc) return;
this.startX = '';
this.startY = '';
this.rect = null;
rectSelf = this;
}
Rect.prototype.down = function(e)
{
var e = e?e:window.event;
rectSelf.startX = e.clientX?e.clientX + document.body.scrollLeft:e.pageX;
rectSelf.startY = e.clientY?e.clientY + document.body.scrollTop:e.pageY;
rectSelf.showRect(true);
}
Rect.prototype.up = function(e)
{
rectSelf.rectBox.style.width = '0px';
rectSelf.rectBox.style.height = '0px';
rectSelf.showRect(false);
}
Rect.prototype.move = function(e)
{
if(rectSelf.rectBox)
{
var currentX = e.clientX?e.clientX + rectSelf.doc.scrollLeft:e.pageX;
var currentY = e.clientY?e.clientY + rectSelf.doc.scrollTop:e.pageY;
rectSelf.rectBox.style.width = Math.abs(currentX - rectSelf.startX) + 'px';
rectSelf.rectBox.style.height = Math.abs(currentY - rectSelf.startY) + 'px';
if(currentX - rectSelf.startX < 0)
{
rectSelf.rectBox.style.left = currentX + 'px';
}
if(currentY - rectSelf.startY < 0)
{
rectSelf.rectBox.style.top = currentY + 'px';
}
//document.title = "left:"+currentX + 'px '+"top:"+currentY + 'px ';
}
}
Rect.prototype.showRect = function(bool)
{
if(bool)
{
if(!this.rectBox)
{
this.rectBox = document.createElement("div");
this.rectBox.id = "rectBox";
document.body.appendChild(this.rectBox);
}
this.rectBox.style.display = "block";
this.rectBox.style.left = this.startX + 'px';
this.rectBox.style.top = this.startY + 'px';
this.addEventListener(this.doc , 'mousemove' , this.move);
}
else
{
if(this.rectBox)
{
this.rectBox.style.display = "none";
}
this.removeEventListener(this.doc , 'mousemove' , this.move);
}
}
Rect.prototype.addEventListener = function(o,e,l)
{
if (o.addEventListener) {
o.addEventListener(e,l,false);
} else if (o.attachEvent) {
o.attachEvent('on'+e,function() {
l(window.event);
});
}
}
Rect.prototype.removeEventListener = function(o,e,l)
{
if (o.removeEventListener) {
o.removeEventListener(e,l,false);
} else if (o.detachEvent) {
o.detachEvent('on'+e,function() {
l(window.event);
});
}
}
window.onload = function()
{
var oRect = new Rect();
oRect.addEventListener(oRect.doc , 'mousedown' , oRect.down);
oRect.addEventListener(oRect.doc , 'mouseup' , oRect.up);
}
</script>
</head>
<body>
<h1> Drag your mouse and a selection box will appear </h1>
</body>
</html>

Hopefully, this article has been helpful in your javascript programming.