javascript - 如何在 JavaScript 中先执行一个 Promise，然后再执行下一个语句

Question

我想要做的是等待第二个 promise 完成，连接数据，即data = data.concat(items)，然后增加计数，使循环运行指定的次数。全部都是用 AngularJS 编写的。

DataService.getSomeData().then(function(data) {
  let count = 1;
  while (count < 3) {
    if (someCondition) { // It evaluates to true

      // Second Promise
      DataService.getUserData().then(function(items) {
        data = data.concat(items); // --------> this should run before incrementing the count
      });

      count++;
    }
    $scope.myData = data;
  }
});

谢谢!

Answer 1

保持 API 返回 promise - 它是最容易处理和最可预测的......

  DataService.getSomeData()
    .then(someData => {
        let count = 1;
        const promises = [];

        while (count < 3) {
            if (someCondition) { // It evaluates to true
                promises.push(DataService.getUserData());
                count++;
            }
        }

        return $q.all(promises)
            .then(data => data.reduce((memo, data) => memo.concat(data), someData));
    })
    .then(data => $scope.myData = data);