Promise實現請求超時處理（基本版）

先是沒有加入請求超時的情況：

 

var http = require('http');

var url = require('url');

 

function get(addr) {

  return new Promise(function(resolve, reject) {

    var url_obj = url.parse(addr);

    var options = {

      hostname: url_obj.hostname,

      path: url_obj.path,

      method: 'GET'

    };

 

    var req = http.request(options, function(res) {

      res.setEncoding('utf8');

 

      var data = '';

      res.on('data', function (chunk) {

        data += chunk;

      });

      res.on('end', function () {

        data = JSON.parse(data);

        resolve(data);

      });

    });

 

    req.on('error', function(e) {

      reject(e)

    });

    req.end();

  });

}

 

get('http://demos.so/result/homework.promise.userInfo').then(function (args) {

  return Promise.all([get('http://demos.so/result/userid=' + args['_id']), get('http://demos.so/result/student=' + args['_id'])]);

}).then(function (args) {

  console.log(args);

}).catch(function(err){

  console.log(err);

});

 

再看一下加入超時的代碼：

 

var http = require('http');

var url = require('url');

 

function delayPromise(ms) {

    return new Promise(function (resolve) {

        setTimeout(resolve, ms);

    });

}

function timeoutPromise(promise, ms) {

    var timeout = delayPromise(ms).then(function () {

            throw new Error('Operation timed out after ' + ms + ' ms');

        });

    return Promise.race([promise, timeout]);

}

 

function get(addr) {

  return new Promise(function(resolve, reject) {

    var url_obj = url.parse(addr);

    var options = {

      hostname: url_obj.hostname,

      path: url_obj.path,

      method: 'GET'

    };

 

    var req = http.request(options, function(res) {

      res.setEncoding('utf8');

 

      var data = '';

      res.on('data', function (chunk) {

        data += chunk;

      });

      res.on('end', function () {

        data = JSON.parse(data);

        resolve(data);

      });

    });

 

    req.on('error', function(e) {

      reject(e)

    });

    req.end();

  });

}

 

timeoutPromise(get('http://demos.so/result/homework.promise.userInfo'),1000).catch(function (err) {

  console.log(err);

}).then(function (args) {

  return Promise.all([timeoutPromise(get('http://demos.so/result/userid=' + args['_id']), 1000), timeoutPromise(get('http://demos.so/result/student=' + args['_id']), 1000)]);

}).then(function (args) {

  console.log(args);

}).catch(function (err) {

  console.log(err);

});

 

 

 

　　原理其實很簡單，就是利用Promise.race，我們先創建一個Promise，里面用setTimeout進行處理，然后將新創建的Promise與我們之前使用的Promise"比賽"一下。