Javascript return after XMLHTTPRequest()

Question

I have this problem, so I want to return the value received after an XMLHTTPRequest(), is this possible? If not, how would I go about achieving the same general idea? Here's what I have so far (It is obviously not working).

function something(url) {
     var temp = getPage(url);
     console.log(temp);
}

function getPage(url) {
     var x = new XMLHTTPRequest();
     x.onload = function() {
          var html = x.responseText;
          //CODE TO PARSE HTML TEXT
          var variable = SOMETHING PARSED FROM HTML
          return variable;
     }
     x.open("GET", url);
     x.send();
}

Andrew Shepherd · Accepted Answer · 2015-05-17 06:31:00Z

1

This is the programming paradigm that every new javascript developer has to deal with.

Because of the asynchronous nature of javascript, functions tend not to pass values back via return statements, but instead the values are passed back via callback methods.

function something(url) {
     getPage(url, function(temp) {
         console.log(temp);
     });
}

function getPage(url, callback) {
     var x = new XMLHTTPRequest();
     x.onload = function() {
          var html = x.responseText;
          //CODE TO PARSE HTML TEXT
          var variable = SOMETHING PARSED FROM HTML
          callback(variable);
     }
     x.open("GET", url);
     x.send();
}

answered May 17, 2015 at 6:31

Andrew Shepherd

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2 Comments

Tomato Over a year ago

If I need multiple call backs like multiple functions that use XMLHTTPRequest after one another, would I just do the same "callback" for each function?

Tomato Over a year ago

for example... somefunction(url, function(res) { callback(res); });

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