Wechat applet development two or three things

How to add background photos

index Upload the background picture under the page folder
wxml in

<image src='./bg1.jpg'></image>

wxss in

image{
    
  position: absolute;
  width: 100%;
  /* height: 50%; */
  display:flex;
 height: 100%;                      
 justify-content: center;
 align-items:center;
}

Used in other components z_index To show the level

How to read DATA Data in

stay index.js Next Page Are there in data data , Want to get the value of the read variable in other functions ：
（data There are array variables in text_list）

var that = this;
var length = that.data.text_list.length;

How to give DATA assignment

After requesting content from the database , You want to assign to data The variables in the ：

var that = this;
that.setData({
    
            text_list : old_data.concat(new_data)
          })

How to center text 、 Word wrap

wxml in
Note that if text Wrap the , Then it will also show a line break

<view class="usermotto" >
    <text class="user-motto" user-select="true">“{
   {motto}}”</text>
</view>

wxss in

.user-motto {
    
  text-overflow:ellipsis; 
  flex-wrap:wrap;
  line-height:25px;
  font-weight: 800;
  /* border: 3rpx solid #6e11ac; */
}
.usermotto {
    
  word-break: break-all;
  display: flex;
  flex-direction: column;
  justify-content: center;
  align-items: center;
  flex-wrap:wrap;
  z-index: 1;
}

How to generate random numbers

//0-9
var random = Math.floor(Math.random() * 10);

How to display the contents of an array at the front end

<block wx:for="{
     {arr}}">
    <view >{
   {index}}:{
   {item.text}}</view>
  </block>

button Click events for

button Binding function in , Such as ：

bindtap="handleTap"

And then in js To realize handleTap function

How to use applet cloud

It must be the official registration number , The test number doesn't seem to work

In the code ：

wx.cloud.init({
    
  env: 'env_id'
})
const db = wx.cloud.database({
    });

How to break through the applet cloud to query at most 20 Restrictions on

Search many times , Splice into the result

 var that = this
    var MAX_LIMIT = 20
    db.collection('db_name').count().then(async res =>{
    
      let total = res.total;
      //  The calculation needs to be divided into several times 
      const batchTimes = Math.ceil(total / MAX_LIMIT)
      console.log("batchTimes:",batchTimes)
      //  Carrying all read operations  promise  Array of 
      for (let i = 0; i < batchTimes; i++) {
    
        await daily5.skip(i * MAX_LIMIT).limit(MAX_LIMIT).get().then(async res => {
    
          let new_data = res.data
          let old_data = that.data.text_list
          // console.log("newdata",new_data)
          that.setData({
    
            text_list : old_data.concat(new_data)
          })
        })
      }
    })