js 顏色值轉換 普通顏色轉透明顏色值

rgb(123,123,123) 轉 rgba(123,123,123, 0.4)

 hexToRgba: function (hex, opacity) {
      var rgb = hex.split('(')[1].split(')')[0].split(',');
      return 'rgba(' + rgb[0].trim() + ',' + rgb[1].trim() + ',' + rgb[2].trim() + ',' + opacity + ')';
    },

#ff0000 轉 rgba(123,123,123, 0.4)

hexToRgba (hex, opacity) {
        return hex && hex.replace(/\s+/g, '').length === 7 ? 'rgba(' + parseInt('0x' + hex.slice(1, 3)) + ',' +
          parseInt('0x' + hex.slice(3, 5)) + ',' +
          parseInt('0x' + hex.slice(5, 7)) + ',' + opacity + ')' : ''
      },