要在JavaScript中进行RGBA与HEX之间的转换，你可以使用以下函数：

1. RGBA到HEX:

   function rgbaToHex(r, g, b, a) {
       r = r.toString(16);
       g = g.toString(16);
       b = b.toString(16);
       a = Math.round(a * 255).toString(16);
   
       if (r.length == 1) r = "0" + r;
       if (g.length == 1) g = "0" + g;
       if (b.length == 1) b = "0" + b;
       if (a.length == 1) a = "0" + a;
   
       return "#" + r + g + b + a;
   }
   

2. HEX到RGBA:

   function hexToRgba(hex) {
       let r = parseInt(hex.slice(1, 3), 16),
           g = parseInt(hex.slice(3, 5), 16),
           b = parseInt(hex.slice(5, 7), 16),
           a = parseInt(hex.slice(7, 9), 16) / 255;
   
       return `rgba(``{r}, ``{g}, ``{b}, ``{a.toFixed(2)})`;
   }
   

使用示例:

• 使用rgbaToHex:

  let hex = rgbaToHex(255, 255, 255, 0.5);  // "#FFFFFF80"
  

• 使用hexToRgba:

  let rgba = hexToRgba("#FFFFFF80");  // "rgba(255, 255, 255, 0.50)"
  

注意: 这里的转换是考虑了透明度（Alpha值）。如果你只需要RGB和HEX之间的转换，可以简单地省略与透明度相关的部分。