CODEWITHSUNDEEP
javascriptmultithreadingconcurrency
Daniel James Bryars
Daniel James Bryars

Reputation: 4621

is there a race condition in this javascript?

In the following js snippet

request = new XMLHttpRequest
request.open('GET', '/my/url', true)
request.send()

request.onload = function() {
  data = JSON.parse(this.response)
}

should the assignment of the on load be before the send() to avoid a race condition. Or does the browser deal with it for you (by firing the on load when you get round to assigning it).

Upvotes: 1

Views: 197

Answers (1)

StackSlave
StackSlave

Reputation: 10617

Your request should look more like:

var request = new XMLHttpRequest || new ActiveXObject('Microsoft.XMLHTTP');
request.open('GET', '/my/url');
request.onreadystatechange = function(){
  if(request.readyState == 4 && request.status == 200){
     console.log(request.responseText);
  }
}
request.send();

To further answer your question request.send() should happen last, because if the response comes back before the function is assigned to request.onreadystatechange, there could be a problem, although it's very unlikely that the response would be that fast.

Upvotes: 1

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