处理$.ajax传递json格式参数，属性为null，undefined，“”

$.ajax传递json格式参数，某属性为null，undefined

function dealNull(obj) {    for (var i in obj) {        if (null == obj[i] || 'null' == obj[i] || undefined == obj[i] || 'undefined' == obj[i] || '' == obj[i]) {            obj[i] = '--';        } else if ('object' == typeof obj[i]) {            dealNull(obj[i]);        }    }};

obj = {ApplicationNo: "AL2017082421251060784", Project_Name: null}

  dealNull(obj)