JS进制颜色转 RGBRGBA 字符串

export const colorToRGB = (val, opa) => {
    var pattern = /^(#?)[a-fA-F0-9]{6}$/; //16进制颜色值校验规则
    var isOpa = typeof opa == 'number'; //判断是否有设置不透明度

    if (!pattern.test(val)) { //如果值不符合规则返回空字符
        return '';
    }

    var v = val.replace(/#/, ''); //如果有#号先去除#号
    var rgbArr = [];
    var rgbStr = '';

    for (var i = 0; i < 3; i++) {
        var item = v.substring(i * 2, i * 2 + 2);
        var num = parseInt(item, 16);
        rgbArr.push(num);
    }

    rgbStr = rgbArr.join();
    rgbStr = 'rgb' + (isOpa ? 'a' : '') + '(' + rgbStr + (isOpa ? ',' + opa : '') + ')';
    return rgbStr;
}