Question

简要说明：在我下面的代码中，ngOnInit()内的opn.success = function()在

之后执行

console.log（“此行首先执行”）;

而我们要先执行opn.onsuccess = function()。

请帮助。

 ngOnInit()
    {
    var opn = indexedDB.open("webDealer", this._globalvar.getvarDBVersion());
        opn.onsuccess = function() {
          var db = opn.result;
          var transac = db.transaction(['usrprfl'], 'readonly');
          var storeNm = transac.objectStore('usrprfl');
          var countRequest = storeNm.count();
          countRequest.onsuccess = function()
          {
            this.cnt = countRequest.result;
            if(this.cnt == 1 )
            {
              storeNm.getAll().onsuccess = function(event)
              {

                var rslt = event.target.result;
                this.usr = rslt[0].nm;
                this.pwd = rslt[0].pw;
                this.clicktyp ='AUTO';

              };
            }
            else
            {
              this.clicktyp ='MANUAL';
            }
          };
          db.close();
        };
console.log("This line is executed first");
    }

    OnLogon()
    {
    //... mycode
    }

Answer 1

对indexedDB.open的调用异步解析。如果希望仅在数据库打开后才显示该日志消息，则需要等待直到数据库打开。现在，您的代码不会等待。

下面是一些等待时间的示例代码：

function open(name, version) {
  return new Promise((resolve, reject) => {
    var request = indexedDB.open(name, version);
    request.onsuccess = _ => resolve(request.result);
    request.onerror = _ => reject(request.error);
  });
}

async function ngOnInit() {
  var db = await open('webDealer', this._globalvar.getvarDBVersion());
  console.log("This line is no longer executed first");
}

函数未执行-IndexedDB，IONIC 2

1 个答案: