javascript position兼容性随笔

if (!window.jasen.core.Position) {
window.jasen.core.Position = {};
}

function Size(width, height) {
this.width = parseFloat(width);
this.height = parseFloat(height);
}

Size.prototype.toString = function () {
return "width=" + this.width + ";height=" + this.height;
}

function Point(x, y) {
this.x = parseFloat(x);
this.y = parseFloat(y);
}

Point.prototype.toString = function () {
return "x=" + this.x + ";y=" + this.y;
}

// 获取窗口的左上角的偏移量（相对屏幕）
function getScreenOffset() {
if (window.screenLeft) {
return new Point(window.screenLeft, window.screenTop);
}
else if (window.screenX) { // Firefox
return new Point(window.screenX, window.screenY);
}

return new Point(0, 0);
}

// 获取屏幕的大小
function getScreenSize() {
return new Size(window.screen.width, window.screen.height);
}

// 获取窗口中的文档显示区的大小
function getVisibleSize() {
if (window.innerWidth) {
return new Size(window.innerWidth, window.innerHeight);
}
else if (document.documentElement && document.documentElement.clientWidth) {
return new Size(document.documentElement.clientWidth, document.documentElement.clientHeight);
}
else if (document.body && document.body.clientWidth) {
return new Size(document.body.clientWidth, document.body.clientHeight);
}

return new Size(0, 0);
}

// 获取窗口中的文档的偏移量（滚动条的值）
function getPageOffset() {
if (window.pageXOffset) {
return new Point(window.pageXOffset, window.pageYOffset);
}
else if (document.documentElement && document.documentElement.scrollLeft) {
return new Point(document.documentElement.scrollLeft, document.documentElement.scrollTop);
}
else if (document.body && document.body.scrollLeft) {
return new Point(document.body.scrollLeft, document.body.scrollTop);
}

return new Point(0, 0);
}

var position = window.Position = window.jasen.core.Position;
position.getScreenOffset = getScreenOffset;
position.getScreenOffsetX = function () { return getScreenOffset().x; };
position.getScreenOffsetY = function () { return getScreenOffset().y; };
position.getScreenSize = getScreenSize;
position.getScreenWidth = function () { return getScreenSize().width; };
position.getScreenHeight = function () { return getScreenSize().height; };
position.getVisibleSize = getVisibleSize;
position.getVisibleWidth = function () { return getVisibleSize().width; };
position.getVisibleHeight = function () { return getVisibleSize().height; };
position.getPageOffset = getPageOffset;
position.getPageOffsetX = function () { return getPageOffset().x; };
position.getPageOffsetY = function () { return getPageOffset().y; };

<script type="text/javascript">
document.body.onclick = function () {
alert(window.Position.getVisibleSize());
alert(window.Position.getPageOffset());
}
</script>