Make GET request inside for loop

最新推荐文章于 2025-05-11 22:38:37 发布

转载最新推荐文章于 2025-05-11 22:38:37 发布 · 345 阅读

本文探讨了如何使用Promise解决JavaScript中异步请求导致的结果打印为空的问题，并提供了两种实现方式：并行请求和顺序请求。

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http://stackoverflow.com/questions/30826474/get-request-inside-of-a-loop-in-javascript

0 down vote favorite

My code:

var locations = {"testurl1", "testurl2"}, results = [];
locations.forEach(function(location,index){
   request.get(location,function (error, response, body){
    if (!error && response.statusCode == 200) {
      var jsonResponse = JSON.parse(body);
      results.add(jsonResponse.address);          
    }
   }
})

console.log(results);

The results are printed as blank due to asynchronous get request. How can i make this work so I have all addresses in results?

Do you want all the get requests to be done at the same time or one after the other? You can do all at once with a forEach loop. forEach works better than a normal for loop because it gives you a new instance of elem and n in each iteration.

object.forEach(function(elem, n) {
  /*Other code */
  $.get(...,function(data){
    //do stuff
  });
});

But if you want to do the requests one after the other you could do it this way.

(function loop(n) {
  if(n >= object.length) return;
  /*Other code */
  $.get(...,function(data){
      //do stuff
      loop(n + 1);
    });
})(0);

http://stackoverflow.com/questions/31367689/make-get-request-inside-for-loop

0 down vote favorite

My code:

var locations = {"testurl1", "testurl2"}, results = [];
locations.forEach(function(location,index){
   request.get(location,function (error, response, body){
    if (!error && response.statusCode == 200) {
      var jsonResponse = JSON.parse(body);
      results.add(jsonResponse.address);          
    }
   }
})

console.log(results);

The results are printed as blank due to asynchronous get request. How can i make this work so I have all addresses in results?

asked Jul 12 at 12:19

mundella
659 3 15 37

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2 Answers

active oldest votes

up vote 0 down vote accepted

Maybe promises can help in this situation. Here is my solution:

'use strict';

var request = require('request');
var Q = require('q');
var defer = Q.defer();
var promise = defer.promise;
var locations = [
  'http://www.google.com', 'http://www.instagram.com'
],
results = [];

locations.forEach(function(location, index) {
  request.get(location, function(error, response, body) {
    if (!error && parseInt(response.statusCode) === 200) {
       results.push(response.statusCode);
    }
    if ((locations.length - 1) === index) {
      defer.resolve();
    }
  });
});

promise.then(function() {
  console.log('RESULTS:', results);
});

I tested this and it's working fine. Promises are briefly explained here.

0 down vote favorite

My code:

var locations = {"testurl1", "testurl2"}, results = [];
locations.forEach(function(location,index){
   request.get(location,function (error, response, body){
    if (!error && response.statusCode == 200) {
      var jsonResponse = JSON.parse(body);
      results.add(jsonResponse.address);          
    }
   }
})

console.log(results);