小程序操作DOM以及JS求取字符串算法(前端网备份)

Posted 2022-01-02 lsc-boke

 //js获取字符串的字节长度
//这套算法一个汉字2字节，字母符号1字节,按一行40个字节算4行
  getLength:function(val)
    var str = new String(val);
    var bytesCount = 0;
    for (var i = 0, n = str.length; i < n; i++) 
      var c = str.charCodeAt(i);
      if ((c >= 0x0001 && c <= 0x007e) || (0xff60 <= c && c <= 0xff9f)) 
        bytesCount += 1;
       else 
        bytesCount += 2;
      
    
    return bytesCount;  
  ,

  onReady: function () 
    var that =this;
    setTimeout(function () 
      //要延时执行的代码
      var query = wx.createSelectorQuery();
      query.select(‘.pContent‘).boundingClientRect()
      query.exec((res) => 
        console.log(res);
        var pContentHeight = res[0].height;
        console.log("ready", pContentHeight);
        if (pContentHeight < 82 || pContentHeight==87) 
          that.setData(
            hidden: true
          );
        
        that.setData(
          pContentHeight: pContentHeight
        );
      )
    ,300) 

  ,

初始化DOM求高度是有BUG的，只能第一次渲染后求，不加延迟有时候求不到值，加了延迟第一面效果不好