the following code, I used to read the database many times, and the data I got was looped, and after the loop, the database was queried. Finally, after resolve, the result I got was only a small part of the data, and the rest of the data was not resolve, but all the data could be printed out through console.log. When resolv was executed, the for loop was not finished.

getProducts(params) {
  return new Promise((resolve, reject) => {
    if (params) {
      this.getDb().then((db: SQLiteObject) => {
        db.transaction((run) => {
          var sql = "SELECT * FROM product_content";
          run.executeSql(sql, [],
            (run, res) => {
              if (res.rows.length != 0) {
                let result = {
                   product_ids: {}
                };
                let retTmp = []
                let exTmp = [1,2,100,600,500,800,900,700,701,300]
                let categoryIds = []
                for (var i = 0; i < res.rows.length; iPP) {
                  var product = res.rows.item(i);
                  categoryIds.push(product.categoryIds)
                  for (var k = 0; k < categoryIds.length; kPP) {
                    var _cid = categoryIds[k]
                    sql = "select id FROM product where category like "%," + _cid + ",%"";
                    run.executeSql(sql, [],
                      (run, res_id) => {
                        if (res_id.rows.length != 0) {
                          for (var i = 0; i < res_id.rows.length; iPP) {
                            var productId = res_id.rows.item(i).ID
                            retTmp.push(productId)
                          }
                        }
                      })
                  }
                }
                // setTimeout(() => {
                  let newRetTmp = Array.from(new Set(retTmp))
                  let newExTmp = Array.from(new Set())

                  if (newExTmp.length > 0) {
                    newRetTmp.map((rettmp, index) => {
                      exTmp.map(extmp => {
                        if (rettmp != extmp) {
                          result.product_ids[newRet] = true
                        }
                      })
                    })
                  }

                  resolve(result);
                // }, 500)
              } else {
                let result = {
                  data: {
                    product_ids: {}
                  }
                };
                resolve(result);
              }
            })
        })
      })
    }
  })
}

I saw the method of using Promise.all () on the Internet before. I modified it to the following code. The code looks fine, but there is no resolve as soon as we get to Promise.all:

getProducts(params) {
  return new Promise((resolve, reject) => {
    if (params) {
      this.getDb().then((db: SQLiteObject) => {
        db.transaction((run) => {
          var sql = "SELECT * FROM product_content";
          run.executeSql(sql, [],
            (run, res) => {
              if (res.rows.length != 0) {
                let result = {
                    product_ids: {}
                };
                let retTmp = []
                let exTmp = [1,2,100,600,500,800,900,700,701,300]
                let categoryIds = []
                let promise = []
                for (var i = 0; i < res.rows.length; iPP) {
promise.push(new Promise((resolve,reject)=>{
                  var product = res.rows.item(i);
                  categoryIds.push(product.categoryIds)
                  for (var k = 0; k < categoryIds.length; kPP) {
                    var _cid = categoryIds[k]
                    sql = "select id FROM product where category like "%," + _cid + ",%"";
                    run.executeSql(sql, [],
                      (run, res_id) => {
                        if (res_id.rows.length != 0) {
                          for (var i = 0; i < res_id.rows.length; iPP) {
                            var productId = res_id.rows.item(i).ID
                            retTmp.push(productId)
                            // this.helperService.console("c0", productId)
                          }
                        }
                      })
                  }
}))
                }
Promise.all(promise).then(res => {
              // setTimeout(() => {
                let ATmp = Array.from(new Set(retTmp))

                if (newExTmp.length > 0) {
                  exTmp.map((rettmp, index) => {
                    newExTmp.map(extmp => {
                      if (rettmp != extmp) {
                        result.product_ids[newRet] = true
                      }
                    })
                  })
                }
                resolve(result);
              // }, 500)
})
                
              } else {
                let result = {
                  data: {
                    product_ids: {}
                  }
                };
                resolve(result);
              }
            })
        })
      })
    }
  })
}

according to the above code, we can"t get the desired results, and the second method is always in the state of pendding. I really don"t know how to solve it. I hope you can give us some advice.