javascript position兼容性随笔

一、Javascript源码

    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; };

二、范例

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