我正在重写一个应用程序,该应用程序分批执行REST API调用,例如一次执行10个,总共执行500个调用。在将使用ES6 +函数的js函数降级为等效于ES5的js函数时,我需要帮助(基本上没有箭头函数或异步/等待)。
在支持ES6 +功能(箭头功能,异步/等待等)的环境中使用的原始应用程序中,我的工作功能如下:
原始功能
:// Async function to process rest calls in batches
const searchIssues = async (restCalls, batchSize, loadingText) => {
const restCallsLength = restCalls.length;
var issues = [];
for (let i = 0; i < restCallsLength; i += batchSize) {
//create batch of requests
var requests = restCalls.slice(i, i + batchSize).map((restCall) => {
return fetch(restCall)
.then(function(fieldResponse) {
return fieldResponse.json()
})
.then(d => {
response = d.issues;
//for each issue in respose, push to issues array
response.forEach(issue => {
issue.fields.key = issue.key
issues.push(issue.fields)
});
})
})
// await will force current batch to resolve, then start the next iteration.
await Promise.all(requests)
.catch(e => console.log(`Error in processing batch ${i} - ${e}`)) // Catch the error.
//update loading text
d3.selectAll(".loading-text")
.text(loadingText + ": " + parseInt((i / restCallsLength) * 100) + "%")
}
//loading is done, set to 100%
d3.selectAll(".loading-text")
.text(loadingText + ": 100%")
return issues
}
例如,到目前为止,我已经正确地编写了代码,将其余的调用在第一个10个组中进行了批处理,但是在解决Promise方面我似乎陷入了困境,因此for循环可以继续迭代。 / p>
我的在制品重写功能:
//Async function process rest calls in batches
function searchIssues(restCalls, batchSize, loadingText) {
const restCallsLength = restCalls.length;
var issues = [];
for (var i = 0; i < restCallsLength; i += batchSize) {
//create batch of requests
var requests = restCalls.slice(i, i + batchSize).map(function(restCall) {
return fetch(restCall)
.then(function(fieldResponse) {
return fieldResponse.json()
})
.then(function(data) {
console.log(data)
response = data.issues;
//for each issue in respose, push to issues array
response.forEach(function(issue) {
issue.fields.key = issue.key
issues.push(issue.fields)
});
})
})
//await will force current batch to resolve, then start the next iteration.
return Promise.resolve().then(function() {
console.log(i)
return Promise.all(requests);
}).then(function() {
d3.selectAll(".loading-text")
.text(loadingText + ": " + parseInt((i / restCallsLength) * 100) + "%")
});
//.catch(e => console.log(`Error in processing batch ${i} - ${e}`)) // Catch the error.
}
//loading is done, set to 100%
d3.selectAll(".loading-text")
.text(loadingText + ": 100%")
return issues
}
我的问题是,完成10个restCall之后,如何正确解决Promise并继续遍历for循环?
作为参考,我尝试使用Babel编译原始函数,但是无法在我的Maven应用程序中进行编译,因此从头开始重写。
答案 0 :(得分:1)
如果没有async/await
,则无法暂停for
循环。但是您可以通过使用递归函数来重现该行为,在每批10之后调用它自己。类似于(未测试)
// Async function to process rest calls in batches
function searchIssues(restCalls, batchSize, loadingText) {
var restCallsLength = restCalls.length,
issues = [],
i = 0;
return new Promise(function(resolve, reject) {
(function loop() {
if (i < restCallsLength) {
var requests = restCalls
.slice(i, i + batchSize)
.map(function(restCall) {
return fetch(restCall)
.then(function(fieldResponse) {
return fieldResponse.json();
})
.then(function(d) {
var response = d.issues;
//for each issue in respose, push to issues array
response.forEach(issue => {
issue.fields.key = issue.key;
issues.push(issue.fields);
});
});
});
return Promise.all(requests)
.catch(function(e) {
console.log(`Error in processing batch ${i} - ${e}`);
})
.then(function() {
// No matter if it failed or not, go to next iteration
d3.selectAll(".loading-text").text(
loadingText + ": " + parseInt((i / restCallsLength) * 100) + "%"
);
i += batchSize;
loop();
});
} else {
// loading is done, set to 100%
d3.selectAll(".loading-text").text(loadingText + ": 100%");
resolve(issues); // Resolve the outer promise
}
})();
});
}