Cannot find function xhrGet in object 

I'm using a javascript calculated value in the attribute. 

but not working here is the code:

var xhrArgs = {
    url: URL_STRING,
    handleAs: "text",
    load: function(data){
      // Replace newlines with nice HTML tags.
      data = data.replace(/\n/g, "<br>");

      // Replace tabs with spaces.
      data = data.replace(/\t/g, "&nbsp;&nbsp;&nbsp;");

      targetNode.innerHTML = data;
    },
    error: function(error){
      targetNode.innerHTML = "An unexpected error occurred: " + error;
    }
  }

  // Call the asynchronous xhrGet
  var deferred = dojo.xhrGet(xhrArgs);