How to display JS string value (dynamic data) in html?

Question

I just want to display the first value of Port01 in Html. The corresponding JavaScript code for this.

<script>


function loadFile(filePath) {
    var result = null;
    var xmlhttp = new XMLHttpRequest();
    xmlhttp.open("GET", filePath, false);
    xmlhttp.send();
    if (xmlhttp.status==200) {
            result = xmlhttp.responseText;
    }
    return result;
  };


var inputData = loadFile("data123.js");
var sensorData = JSON.parse(inputData);
var valueData = sensorData[0].value;
document.getElementById("value").innerHTML = valueData;
</script>

<body>
    <div id="value" ></div>
</body>

and in addition data123.js file

[{"name":"VVB001 (port01)","time":"2021-02-10 14:01:09","type":"a-Peak","value":0.2},{"name":"VVB001 (port02)","time":"2021-02-10 14:01:09","type":"a-Peak","value":0.2},{"name":"VVB001 (port03)","time":"2021-02-10 14:01:09","type":"a-Peak","value":0}]

Wais Kamal · Accepted Answer · 2021-02-10 17:44:43Z

1

The problem here is that the following line:

result = xmlhttp.responseText;

gets executed before the response arrives. This is because of the asynchronous nature of the call, which you set with false in xmlhttp.send(). You should wrap the above line in an onreadystatechange listener:

function loadFile(filePath) {
  var result = null;
  var xmlhttp = new XMLHttpRequest();
  xmlhttp.open("GET", filePath, false);
  xmlhttp.send();
  xmlhttp.onreadystatechange = function() {
    if (xmlhttp.status == 200) {
      result = xmlhttp.responseText;
      return result;
    }
  };
};

var inputData = loadFile("data123.js");
var sensorData = JSON.parse(inputData);
var valueData = sensorData[0].value;
document.getElementById("value").innerHTML = valueData;

A side note: your JSON file has a .js extension.

answered Feb 10, 2021 at 17:44

Wais Kamal

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3 Comments

Wais Kamal Over a year ago

Then the JSON you are getting is invalid, as opposed to that you've posted in your question, which is valid.

Lutetia87 Over a year ago

other ideas maybe?

Wais Kamal Over a year ago

This is what can be deduced from your error.

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