jquery 实现loading

 通常function 的方法名称大写 代表时构造函数。需要通过new 关键字调用。

function ShowLoading(opt) {
    //默认配置项
    var _default = {
        "target": "body", //需要展示的遮罩的目标
        "cssName": "_showloading", //class名称，可以自定义class
        "loadingImg": "/static/themes/vocs/ui-images/loading.gif", //遮罩图片的路径
        "loadingText": "数据正在加载,请稍后...", //提示层的提示文字
        "hideCall": null, //关闭回调函数
        "timeout": 0 //是否自动关闭
    };
    $.extend(this, _default, opt);
    if (typeof this.target == "string")
        this.target = $(this.target);
    if (typeof context != 'undefined')
        this.loadingImg = context + this.loadingImg;
    var me = this;
    var isBody = $(me.target).prop("nodeName") == "BODY";
    //获取目标的大小
    var getSize = function () {

        var scrollTop = isBody ? $(window).scrollTop() : $(me.target).scrollTop();
        var scrollLeft = isBody ? $(window).scrollLeft() : $(me.target).scrollLeft();
        //var w = isBody ? (scrollLeft+$(window).width()) : (scrollLeft+$(me.target).width());
        //var h = isBody ? (scrollTop + $(window).height()) : (scrollTop + $(me.target).height());
        var w = isBody ? ($(window).width()) : ($(me.target).width());
        var h = isBody ? ($(window).height()) : ($(me.target).height());
        return { w, height: h, scrollTop: scrollTop, scrollLeft: scrollLeft};
    }
    var setPsIntv;
    var $loading;
    this.show = function (msg, callBack) {

        if (!$loading) {
            this.loadingId = "_load" + (new Date()).valueOf();
            if (!isBody)
                $(me.target).css("position", "relative");
            $loading = $("<div>", {
                "id": this.loadingId,
                "class": this.cssName,
                //"style": "border:1px solid red",
                "html": "<div class='" + this.cssName + "-msg'  style='background-image:url(" + this.loadingImg + ");background-repeat: no-repeat;background-position: 5px 10px;text-indent:25px;'>" + this.loadingText + "</div>"
            }).appendTo(this.target);
            var setPostion = function () {
                $loading.css({
                    //  getSize().width + "px",
                     getSize().width + "px",
                    height: getSize().height + "px",
                    top: getSize().scrollTop + "px",
                    left: getSize().scrollLeft + "px"
                });
                var sefWidth = $loading.children().width(),
                    sefHeight = $loading.children().height();
                $loading.children().css({
                    "top": function () {
                        return parseInt((getSize().height- sefHeight) / 2) + "px"
                    },
                    "left": function () {
                        return parseInt((getSize().width - sefWidth) / 2) + "px"
                    }
                })

            }

            setPsIntv = setInterval(function () {
                setPostion();
            }, 50);


        }
        if (msg){
            this.loadingText = msg;
            $loading.children().text(msg);
        }


        //是否有回调函数
        if (callBack != undefined && typeof callBack == "function") {
            this.hideCall = callBack;
        }
        //是否是定时关闭
        if (this.timeout > 0) {
            setTimeout(function () {
                me.hide();
            }, this.timeout);
        }
        return this;
    };
    this.hide = function () {
        if ($loading) {
            $loading.remove();
        }
        if (typeof this.hideCall=="function") {
            this.hideCall();
        }
        if (setPsIntv)
            clearInterval(setPsIntv);
    };
}

 这是构造函数 使用方式如下

var loading=new ShowLoading();
loading.show();

为了不写new 我们通常这样：

function showLoading(opt) {
    var loading = new ShowLoading(opt);
    loading.show();
    return loading;
}

每次调用就很方便了：

var loading = showLoading();

setTimeout(function () {
    loading.hide();
}, 1500);

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