Change the source of a JSON file, without reloading the page?

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Javascript

HTML

jQuery

I have the following code, how can I get the src of the json data to change when the user submits a form? I need to change the 'text=' part of the src, to what the user has entered in the form, without a page reload.

<script>
function myFunction(arr) {
	
        var i =0;
        document.getElementById("fullname").innerHTML =  arr[i].FULLNAME ;
        document.getElementById("motto").innerHTML =  "'"+arr[i].MOTTO+"'";
        ...
        ...
        document.getElementById("firstlog").innerHTML = arr[i].FIRSTLOGIN;
        document.getElementById("lastact").innerHTML = arr[i].LASTACTIVITY;
		}
});
</script>
<script src="http://nsdata.a78.org/m/json.php?text=southern_ageena&type=json"></script>