From http://www.w3schools.com (Copyright Refsnes Data)
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Before sending data off to a server, we will look at three important properties of the XMLHttpRequest object.
After a request to a server, we need a function to receive the data returned from the server.
The onreadystatechange property stores the function that will process the response from a server. The function is stored in the property to be called automatically.
The following code sets the onreadystatechange property and stores an empty function inside it:
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xmlhttp.onreadystatechange=function() { // We are going to write some code here } |
The readyState property holds the status of the server's response.
Each time the readyState property changes, the onreadystatechange function will be executed.
Possible values for the readyState property:
| State | Description |
|---|---|
| 0 | The request is not initialized |
| 1 | The request has been set up |
| 2 | The request has been sent |
| 3 | The request is in process |
| 4 | The request is complete |
Add an If statement to the onreadystatechange function to test if the response is complete (means that now we can get our data):
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xmlhttp.onreadystatechange=function() { if(xmlhttp.readyState==4) { // Get data from the server's response } } |
The data sent back from a server can be retrieved with the responseText property.
Now, we want to set the value of the "Time" input field equal to responseText:
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xmlhttp.onreadystatechange=function() { if(xmlhttp.readyState==4) { document.myForm.time.value=xmlhttp.responseText; } } |
The next chapter shows how to ask a server for data!
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From http://www.w3schools.com (Copyright Refsnes Data)