等待里面有一個承諾的 forEach 完成

Question

我在等待我的 forEach 循環（里面有一個承諾）完成時遇到了問題。 我找不到任何真正的解決方案，這會使腳本等到結束，然后再繼續執行。 我無法使 someFunction 同步。

makeTree: function (arr) {
    arr.forEach(function (resource) {
        someModule.someFunction(resource).then(function () { //a Promise
            //do something with the resource that has been modified with someFunction
        });
    });
    // do something after the loop finishes
}

Answer 1

而不是forEach()使用map()創建一個承諾數組，然后使用Promise.all()

let promiseArr = arr.map(function (resource) {
    // return the promise to array
    return someModule.someFunction(resource).then(function (res) { //a Promise
        //do something with the resource that has been modified with someFunction
        return res;
    })
});

Promise.all(promiseArr).then(function(resultsArray){
   // do something after the loop finishes
}).catch(function(err){
   // do something when any of the promises in array are rejected
})

Answer 2

嘗試這個，

makeTree: function (arr) {
   var promises = [];
   arr.forEach(function(resource) {
      promises.push(someModule.someFunction(resource));
   });
   Promise.all(promises).then(function(responses) {
      // responses will come as array of them
      // do something after everything finishes
   }).catch(function(reason) {
      // catch all the errors
      console.log(reason);
   });
}

您可以通過簡單示例參考此鏈接以獲取有關Promise.all更多信息。