js判断是否为空

软类型语言值为0 null false undefined等为假 否则为真

$(document).ready(function() {
            $(window).bind("scroll", scrollTrigger);
            window.setTimeout(loadPage, 500);
            loadStat();

            var i = 0 ;
            var isnull = null;
            var isfalse = false;
            if(!i){
                alert("true");
            }
            if(!isnull){
                alert("true");
            }
            if(!isfalse){
                alert("true");
            }
        });

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