为什么语句在数据库事务之前执行？

Question

in below code, I want to set state domains after all the DB transaction completed in my code, please any one tell me to do that operation perfect.

I calling below method to set the new domains array

setFavorites() {
    var arr = this.state.domains.map((item, index) => {
        new Promise((resolve, reject) => {
            db.transaction((tx) => {
                try {
                    tx.executeSql(
                        'SELECT * FROM table_favorites WHERE id=' + item.product_id, [],
                        (tx, results) => {
                            var len = results.rows.length;
                            if (len > 0) { item.isFavorite = true } else { item.isFavorite = false }
                        }
                    );
                    resolve()
                } catch (error) {
                    reject(error)
                }
            });
        })
        return { ...item }
    })
    this.setState({ domains: arr })
}

Answer 1

I would recommend use Promise.all() and inside the.then use the setState()

something like:
EDIT : this.state.domains is array of object, so it should not be updated directly

setFavorites() {
  Promise.all(
      this.state.domains.map(item => {
          return new Promise((resolve, reject) => {
              db.transaction((tx) => {
                  try {
                      tx.executeSql(
                          'SELECT * FROM table_favorites WHERE id=' + item.product_id, [],
                          (tx, results) => {
                              var len = results.rows.length;
                              if (len > 0) {
                                resolve({...item, isFavorite = true})
                              }
                              else {
                                resolve({...item, isFavorite = false})
                              }
                          }
                      );
                      
                  } catch (error) {
                      reject(error)
                  }
              });
          })
      })
  )
  .then(arr => this.setState({ domains: arr })) 
}