所以，我正在尝试使用节点和请求运行服务器测试功能。我的目标是运行一组服务器对象，构建成功服务器ping的数组，并返回具有最佳优先级的单个数组（硬编码到服务器对象中）。到目前为止，这是我的代码：
//brings in http script availability
var request = require('request');
//set of test servers
var serverSet = [
{
"url": "http://doesNotExist.askdex.co",
"priority": 1
},
{
"url": "http://tricon.co",
"priority": 7
},
{
"url": "http://offline.bing.co",
"priority": 2
},
{
"url": "http://google.com",
"priority": 4
},
{
"url": "http://yahoo.com",
"priority": 6
}
];
//inform user of process taking place
console.log("We are about to test some server requests for you, please stand by.");
function serverTest(url, priority) {
//creates options to allow for request timeout
var options = {
url: url,
timeout: 5000
};
return new Promise (
function(resolve, reject) {
request(options, function(err, res, body) {
//if (err) {console.log("There was an error: " + err)};
//test if server responds with a positive status
if (res !== undefined) {
if (res.statusCode >= 200 && res.statusCode <= 299) {
//console.log("response from online server is " + res.statusCode);
resolve({"url": url, "priority": priority});
} else
if (res.statusCode >= 300 && res.statusCode <= 399) {
//console.log("response from redirected server is " + res.statusCode);
reject("The server is not working");
} else
if (res.statusCode >= 400 && res.statusCode <= 499) {
//console.log("response from not working server is " + res.statusCode);
reject("The server is broken");
}//==> end of inner if/else statement
} else {
reject("Server is unresponsive");
}//==> end of outer if/else statement
});//==> end of get request
}
);
};
//call of function to run program
//var test0 = serverTest(serverSet[0].url, serverSet[0].priority).then(function(resolve){console.log("resolution is: "+ JSON.stringify(resolve))}).catch(function(reject){console.log(reject)});
//console.log("Test0: "+ test0);
//var test1 = serverTest(serverSet[1].url, serverSet[1].priority).then(function(resolve){console.log("resolution is: "+ JSON.stringify(resolve))}).catch(function(reject){console.log(reject)});
//console.log("Test1: "+ JSON.stringify(test1));
//var test2 = serverTest(serverSet[2].url, serverSet[2].priority).then(function(resolve){console.log("resolution is: "+ JSON.stringify(resolve))}).catch(function(reject){console.log(reject)});
//console.log("Test2: "+ JSON.stringify(test2));
//var test3 = serverTest(serverSet[3].url, serverSet[3].priority).then(function(resolve){console.log("resolution is: "+ JSON.stringify(resolve))}).catch(function(reject){console.log(reject)});
//console.log("Test3: "+ test3);
//var test4 = serverTest(serverSet[4].url, serverSet[4].priority).then(function(resolve){console.log("resolution is: "+ JSON.stringify(resolve))}).catch(function(reject){console.log(reject)});
//console.log("Test4: "+ JSON.stringify(test4));
function findServer(array) {
var build = [];
return new Promise (
function(resolution, rejection) {
array.forEach(function(server){
serverTest(server.url, server.priority)
.then(function(resolve){
if (typeof resolve === "object") {
console.log("findServer resolve = " + JSON.stringify(resolve));
build.push(resolve);
console.log("build = " + JSON.stringify(build));
return build;
}
})
.catch(function(error){
//console.log("Error: " + error);
});
});
resolution(build);
// if (onlineServers.length == 0) {
// //console.log("No online servers.");
// reject('Error: No servers are online.');
// }//==> end of if statement
}
)
};
findServer(serverSet).then(function(result) {
console.log("The result is " + JSON.stringify(result));
}).catch(function(error){
console.log("The error is " + error);
});
// function findServer(array) {
// return new Promise (
// function(resolution, rejection) {
// var build = [];
// array.forEach(function(server){
// serverTest(server.url, server.priority).then(function(resolve){
// if (typeof resolve === "object") {
// console.log("findServer resolve = " + JSON.stringify(resolve));
// build.push(resolve);
// console.log("build = " + JSON.stringify(build));
// resolution(build);
// }
// }).catch(function(error){
// //console.log("Error: " + error);
// });
// });
// // if (onlineServers.length == 0) {
// // //console.log("No online servers.");
// // reject('Error: No servers are online.');
// // }//==> end of if statement
// }
// )
// };
// findServer(serverSet).then(function(result){
// console.log(result);
// console.log(onlineServers);
// //condition check and modification if more than one server response is successful
// if (result.length > 1) {
// result.sort(function(a,b){
// return a.priority - b.priority;
// })
// console.log(result[0].url + " has the lowest available priority.");
// } else {
// console.log(result[0].url + " has the lowest available priority.");
// }//==> end of if statement
// }).catch(function(error){
// console.log(error);
// });
注释掉的代码包含许多尝试来测试和找出使其工作的其他方法。
答案 0 :(得分：1)
您希望使用Promise.all()等待许多Promise一直解决，直到继续，但请注意这个警告（强调我的）：
Promise.all（iterable）方法返回一个解析时间的promise 可迭代参数中的所有promise都已解决，或拒绝 由于第一个通过的承诺拒绝。
因此，在您的情况下，您需要确保传递给.all()的所有承诺都将得到解决。为此，您可以使用Promise.catch()处理来自serverTest()功能的拒绝并继续优雅地继续。
如果onRejected抛出一个，则catch（）返回的Promise被拒绝 错误或返回一个本身被拒绝的Promise; 否则，它是 解决。
var serverSet = [{
"url": "http://doesNotExist.askdex.co",
"priority": 1
}, {
"url": "http://tricon.co",
"priority": 7
}, {
"url": "http://offline.bing.co",
"priority": 2
}, {
"url": "http://google.com",
"priority": 4
}, {
"url": "http://yahoo.com",
"priority": 6
}]
function serverTest(url, priority) {
var options = {
url: url,
timeout: 5000
}
return new Promise((resolve, reject) => {
// Always resolve for testing purposes
resolve({
"url": url,
"priority": priority
})
})
}
function findServer(servers) {
var build = []
var promises = servers.map(server => {
return serverTest(server.url, server.priority)
.then(resolve => {
// Do your validation of resolve here
build.push(resolve)
})
.catch(error => {
// By using catch, you ensure this promise chain will continue to
// resolve as long as you don't throw an error here or return another
// Promise that will reject
console.log("Server " + server.url + " failed with : " + error)
})
})
return Promise.all(promises).then(values => {
// At this point you know that all your promises have resolved, and
// the successful ones have added an element to 'build'
return build
});
};
findServer(serverSet).then(result => {
console.log("result is : " + JSON.stringify(result))
})
修改：使用map()代替forEach + push()，感谢评论中的建议。
编辑2：添加了完整示例的代码，但修改了serverTest以便它始终解析，以验证findServer是否正确填充了build数组。