[英]Async await on array data
由於某種原因,我的異步調用沒有按預期工作。 這是我正在嘗試做的事情:
var authcodes = ["E06000001","E06000002","E06000003"];
var dict = [];
async function ajaxCall() {
for(var i=0;i<authcodes.length;i++){
$.ajax({
type: "GET",
url: 'https://api.coronavirus.data.gov.uk/v1/data?filters=areaCode=' + authcodes[i] +'&structure={"areaCode":"areaCode","cumCasesByPublishDate":"cumCasesByPublishDate"}',
dataType: "json",
success: function(data) {
dict.push(data.data[0].cumCasesByPublishDate);
}
});
} return dict;
}
async function printArr () {
const someApiRes = await ajaxCall()
console.log(someApiRes[1]); //this doesn't work
console.log(dict[1]); //this doesn't work
}
printArr();
這是帶有注釋代碼的 JSFiddle: https://jsfiddle.net/gjv9hrpo/1/
我知道 printArr printArr()
function 必須在陣列填充后運行,因為我希望等待能夠解決的async
性質。 我用錯了嗎?
謝謝。
使用 promise.All()
async function ajaxCall() {
var promises = [];
for(var i=0;i<authcodes.length;i++){
promises.push($.ajax({
type: "GET",
url: 'https://api.coronavirus.data.gov.uk/v1/data?filters=areaCode=' + authcodes[i] +'&structure={"areaCode":"areaCode","cumCasesByPublishDate":"cumCasesByPublishDate"}',
dataType: "json",
success: function(data) {
dict.push(data.data[0].cumCasesByPublishDate);
}
}));
}
await Promise.all(promises);
return dict;
}
用 Promise 來做這件事可能更有意義。
Promise.all讓您知道所有輸入承諾何時已履行或其中一個承諾何時拒絕。
var authcodes = ["E06000001", "E06000002", "E06000003"]; function ajaxCalls() { return Promise.all( authcodes.map((code) => { return new Promise(async (resolve) => { const response = await fetch( `https://api.coronavirus.data.gov.uk/v1/data?filters=areaCode=${code}&structure={"areaCode":"areaCode","cumCasesByPublishDate":"cumCasesByPublishDate"}` ) const json = await response.json(); resolve(json.data[0].cumCasesByPublishDate); }); }) ); } function printArr() { ajaxCalls().then((values) => { console.log(values); }).catch(e => { console.error(e) }); } printArr();
Promise.allSettled會在所有輸入承諾都已結算時向您發出信號,這意味着它們要么被履行,要么被拒絕。 這在您不關心 promise 的 state 的情況下很有用,您只想知道工作何時完成,而不管它是否成功。
var authcodes = ["E06000001", "E06000002", "E06000003"]; function ajaxCalls() { return Promise.allSettled( authcodes.map((code, i) => { return new Promise(async (resolve, reject) => { if (i ===0 ) reject('something went wrong') const response = await fetch( `https://api.coronavirus.data.gov.uk/v1/data?filters=areaCode=${code}&structure={"areaCode":"areaCode","cumCasesByPublishDate":"cumCasesByPublishDate"}` ); const json = await response.json(); resolve(json.data[0].cumCasesByPublishDate); }); }) ); } async function printArr() { const results = await ajaxCalls(); console.log(results.map((result) => result.value || result.reason)); } printArr();
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