表单验证 点击确认发布不能为空错误提示 
以下是效果图：

代码如下：

WXML:

1. [html] view plain copy print?在CODE上查看代码片派生到我的代码片
2. <view class="ad_popError" wx:if="{{popErrorMsg}}">{{popErrorMsg}}</view>
3. <view class="ad_popFt">
4. <form bindsubmit="goDetail" >
5. <textarea class="ad_popArea" bindinput="commentTxtFn" focus="{{isPopOpen}}" placeholder="请输入留言内容" placeholder-style="color:#cccccc;" name="textarea" />
6. <view class="ad_popCout">
7. <text class="one_star">你还可以输入</text>
8. <text class="one_stars {{!!tips?'danger':''}}">{{commentTxtCount}}</text>
9. <text class="one_star">字</text>
10. </view>
11. <button class="informBtn" form-type="submit">确认发布</button>
12. </form>
13. </view>

WXSS:

1. [css] view plain copy print?在CODE上查看代码片派生到我的代码片
2. page{background: #f4f4f4;}
3. .ad_popHd{height: 76rpx; line-height: 76rpx; font-size: 32rpx;text-align: center; border-bottom: 1px solid #cdd1cd; padding: 0 20rpx;color: #202120;}
4. .ad_popFt{ margin: 20rpx ; margin-top: 50rpx;}
5. .ad_popArea{ width: 708rpx; height:400rpx;font-size:30rpx;padding: 20rpx; box-sizing: border-box; -webkit-box-sizing: border-box; line-height: 40rpx; color: #333; background: #fff; }
6. .ad_popCout{ color: #969899; font-size: 24rpx; text-align: right; line-height: 58rpx; padding: 0 20rpx;}
7. .informBtn{background: #09bb07;color: #fff;font-size: 34rpx; margin-top: 38rpx;height: 88rpx;}
8. .one_stars{color: #999;}
9. .one_star{font-size: 20rpx;color: #999;}
10. .danger{ color: #f64400;}
11. .ad_popError{ background: #de352d; color: #fff; height: 58rpx; line-height: 58rpx; font-size: 24rpx; text-align: center; position: absolute; left: 0; top: 0; width: 100%; z-index:3;}

JS:

1. [javascript] view plain copy print?在CODE上查看代码片派生到我的代码片
2. // pages/informLeaveMsg/informLeaveMsg.js
3. Page({
4.  
5. /**
6. * 页面的初始数据
7. */
8. data: {
9.  
10. },
11. //确认发布
12. goDetail:function(e){
13. setTimeout(()=>{
14. var subValue = e.detail.value.textarea
15. console.log(subValue)
16. if (subValue == null || subValue == "") {
17. console.log("不能为空")
18. this.setData(
19. { popErrorMsg: "发布的留言内容不能为空" }
20. );
21. this.ohShitfadeOut();
22. return;
23. }
24.  
25. },100)
26.  
27. },
28.  
29. ohShitfadeOut() {
30. var fadeOutTimeout = setTimeout(() => {
31. this.setData({ popErrorMsg: '' });
32. clearTimeout(fadeOutTimeout);
33. }, 3000);
34. },
35.  
36. })