js获取PHP传过来的值如果为空或者为null或者为undefined

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如果不设置js的值

那么编辑时页面会出现  可能是  null 或者undefined

 var swd_id = $(t).attr("id-data"); //商品id
        SWD_ID = swd_id;
        var a_price = $(t).attr("aprice-data"); //渠道价
        var c_price = $(t).attr("cprice-data"); //修理厂价

        var cost_price = $(t).attr("cost-data"); //修理厂价

        var w_name = $(t).attr("wname-data");  //商品名称

        var oe = $(t).attr("oe-data");  //oe
        var description = $(t).attr("description-data");  //车型备注
        var mcode = $(t).attr("mcode-data");  //mcode 助记码
        var rem = $(t).attr("rem-data");  //备注

        if(oe == "" || oe=== "undefined" || oe === "null"){
            var oe="";
        }
        if(description == "" || description === "undefined" || description === "null"){
            var description="";
        }
        if(rem == "" || rem=== "undefined" || rem === "null"){

            var rem ="";
        }
        if(mcode == "" || mcode=== "undefined" || mcode === "null"){

            var mcode="";
        }
        $("#costprice").val(cost_price);
        $("#aprice").val(a_price);
        $("#cprice").val(c_price);
        $("#wname").val(w_name);
        $("#oe").val(oe);
        $("#description").val(description);
        $("#rem").val(rem);
        $("#mcode").val(mcode);

当时 oe== undefined || oe == null  就一直出现页面的null  或者是undefined 

这里一定要使用  全等于 的