html怎么让文字半透明,用js设置div背景半透明而文字不透明

这里用js来实现元素半透明，而其中的文字正常显示的方法：// 把16进制颜色转换成rgb格式

var colorToRGB = function (color) {
var reg = /^#([0-9a-fA-f]{3}|[0-9a-fA-f]{6})$/g;

var sColor = color.toLowerCase();

if (sColor && reg.test(sColor)) {
if (sColor.length === 4) {
var sColorNew = "#";

for (var i = 1; i

sColorNew += sColor.slice(i, i + 1).concat(sColor.slice(i, i + 1));

}

sColor = sColorNew;

}

//处理六位的颜色值

var sColorChange = [];

for (var i = 1; i

sColorChange.push(parseInt("0x" + sColor.slice(i, i + 2)));

}

return sColorChange.join(",");

} else {
return color;

}

}

var setBakckgoundAndOpacity = function (obj, color, opacity) {
var rgbaObj = colorTo