js 判断数据是否为空 // var a = ""; // var a = " "; // var a = null; // var a = undefined; // var a = []; // var a = {}; // var a = NaN; if(a === undefined) { // 只能用 === 运算来测试某个值是否是未定义的 console.log("为undefined"); } if(a == null) { //
浏览器控制台的js采集数据结果持久化存储 how to open a file in javascript https://developer.mozilla.org/en-US/docs/Web/API/File https://stackoverflow.com/questions/6396101/pure-javascript-send-post-data-without-a-form https://developer.mozilla.org/en-US/docs/Web/API/XML