javascript - Why is this function not waiting until it has data from XHR request? -


when call getcurrentconditions tries return data before requestdata has completed , therefore doesn't find data.currently. definately getting data returned url, have tried adding timeout loop wait xhr load, broke script together. kind of confused why second function not waiting this.requestdata(latitude, longitude); finish before continuing.

this.requestdata = function(latitude, longitude) {     request_url = self.api_endpoint + api_key + '/' + latitude + ',' + longitude + '?units=auto';     var xhr = new xmlhttprequest();     xhr.onreadystatechange = function() {         if(xhr.readystate==4 && xhr.status==200) {             content = xhr.responsetext;             if(content != '' && (content)) {                 return json.parse(content);             } else {                 return false;             }         }     }     xhr.open('get', 'proxy.php?url='+request_url, true);     xhr.send(null); } /**  * return current conditions  *  * @param float $latitude  * @param float $longitude  * @return \forecastioconditions|boolean  */ this.getcurrentconditions = function(latitude, longitude) {     data = this.requestdata(latitude, longitude);     if(data !== false) {         return new forecastioconditions(data.currently);     } else {         return false;     } }    var forecast = new forecastio(api_key); var condition = forecast.getcurrentconditions(latitude, longitude);

because ajax asynchronous, means once request sent continue executing without waiting response.

one easy solution turn off asynchronous nature passing 3rd parameter .open() method false, has drawbacks browser thread blocked till request completed means ui remain unresponsive till request completed.

xhr.open('get', 'proxy.php?url='+request_url, false);

the correct solution use callback method

this.requestdata = function(latitude, longitude, callback) {     request_url = self.api_endpoint + api_key + '/' + latitude + ',' + longitude + '?units=auto';     var xhr = new xmlhttprequest();     xhr.onreadystatechange = function() {         if(xhr.readystate==4 && xhr.status==200) {             content = xhr.responsetext;             if(content != '' && (content)) {                 callback(json.parse(content));             } else {                 callback(false);             }         }     }     xhr.open('get', 'proxy.php?url='+request_url, true);     xhr.send(null); } /**  * return current conditions  *  * @param float $latitude  * @param float $longitude  * @return \forecastioconditions|boolean  */ this.getcurrentconditions = function(latitude, longitude, callback) {     this.requestdata(latitude, longitude, function(data) {         if(data !== false) {             callback(forecastioconditions(data.currently));         } else {             callback(false);         }     }); }    var forecast = new forecastio(api_key); forecast.getcurrentconditions(latitude, longitude, function(condition){     if(condition !== false) {      } else {      } });

Comments

Post a Comment

Popular posts from this blog

Why does Ruby on Rails generate add a blank line to the end of a file? -

running rails generate controller foo home results in: class foocontroller < application controller def home end end (there's nothing on line in actual file, blank line) is there purpose blank line? it's common use newline indicate end of line, last line. many editors (like vi, use) add in newline silently. consensus text files (especially in unix world) should end in newline, , there have been problems historically if wasn't present. why should text files end newline? the tool used count lines in file "wc" counts newlines in file, without trailing newline show 3 instead of 4. it improves readability of templates used in generator. consider: https://github.com/rails/rails/blob/master/railties/lib/rails/generators/rails/controller/templates/controller.rb to remove trailing newline, template have last line of: end<% end -%> instead of: end <% end -%> that seems less readable me. the discussion below refers ...
Read more

node.js - Bad Request - node js ajax post -

i'm using express 3.0 , node v0.11.0. have button submits form , i'm using ajax post data json object node server. client code is: $('#contact').submit(function(e) { console.log('submit called'); var formdata = json.stringify($('form').serializeobject()); console.log(formdata); $.ajax({ url: "http://localhost:3000/savedata/", type: "post", datatype: 'json', data: {objectdata: formdata}, contenttype: "application/json", complete: function() { console.log('process complete'); }, success: function(data) { console.log('process sucess'); }, error: function() { console.log('process error'); }, }); return false; }); then on server: var express = require('express'); var app = express(); app.set('views', __dirname + '/views'); app.set('view engine', 'jade'); app.use(express.bodyparser());...
Read more

keyboard - Smiles and long press feature in Android -

i've created android keyboard. how add features inserting smilies, , using long keypresses display symbols? to create long-press behavior allows select several options pop-up menu, follow guide (specifically pop-up menu section): http://developer.android.com/guide/topics/ui/menus.html smileys (also known emoticons) combination of keys, understood programs , parsed same way. have do, when clicks smiley face on keyboard, simulate pressing of key combination matching emoticon. example, when clicks smiley, should simulate key presses ':' , ')' :). here's list of emoticons: http://en.wikipedia.org/wiki/list_of_emoticons
Read more