js数组和集合互转可用于去重: 数组转集合 var arr = [55, 44, 65]; var set = new Set(arr); console.log(set.size === arr.length); console.log(set.has(65)); 集合转数组 var set = new Set([1, 2, 3, 3, 4]); Array.from(set) //输出[1,2,3,4]
先引出一个问题:通过调用getElements*()这样的方法返回来类(伪)数组,能对其本身的元素进行排序吗? 答案是不能,因为这些对象的都是NodeList . NamedNodeMap 或 HTMLCollection的实例.他们都是“动态的”.所谓动态就是每次调用实例上的方法,都会运行一次基于文档的查询.下面的代码会造成死循环 1 var oDivs = document.getElementsByTagName("div"); 2 for (var i = 0; i <
截取七牛上传图片的后缀名: export function getInputKey(info){ let self = this; let obj = JSON.parse(info); let qiniuKey; let imaName; let imgSuffix; if(obj){ qiniuKey = obj.key; imaName = obj.fileName; imgSuffix = imaName.substring(imaName.lastIndexOf('.') + 1);
//https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String//返回对应索引的字符 chartAt() //返回对应所引的字符的统一码(Unicode value) charCodeAt() //Returns a non-negative integer that is the UTF-16 encoded code point value at the given posit