一些工作知识点记录

//使用promise封装ajax

function _ajax(url){
    
    
    var promise = new Promise(function(resolve,reject){
    
    
            var XHR = XMLHttpRequest? new XMLHttpRequest() ? new Window.ActiveXObject('Microsoft.XMLHTTP');
            XHR.onreadystatechange = function(){
    
    
                if(XHR.readyState == 4){
    
    
                    if((XHR.status >= 200 && XHR.status<300 ) || XHR.status == 304){
    
    
                        try{
    
    
                            var response = JSON.parse(XHR.responseText);
                            resolve(response)
                        }catch(e){
    
    
                            reject(e)    
                        }
                    }else{
    
    
                        reject(new Error("request error:"+XHR.statusText))
                    }
                }
            }
            XHR.open('GET',url,true);
            XHR.send();
    })
    return promise;
   
}
//调用
_ajax(url).then((res)=>{
    
    console.log(res)})//使用promise封装

css使用伪类after在每个标签后面增加图标 比如筛选的每个选项 选中时候末尾变成勾子图标

```css
.filter-panel .active::after{
    
    
  content:'';
  width:40rpx;
  height:40rpx;
  float:right;
  margin-top:20rpx;
  background-repeat:no-repeat;
  background-size: cover;
  background-image:url("data:image/svg+xml;utf8,<svg xmlns='http://www.w3.org/2000/svg' width='256' height='256' viewBox='0 0 48 48' fill='rgba(36, 103, 241, 1)'><path d='M0 0h48v48H0z' fill='none'></path><path d='M18 32.34L9.66 24l-2.83 2.83L18 38l24-24-2.83-2.83z'></path></svg>");
  
}