How to change iframe src to be variable

I'm using the following code inside HTML embedded component to display the following URL

"https://datastudio.google.com/embed/reporting/fkfkfkfkfffkkf/page/gurVC"

I received this URL from the following function (inside the code)

<script type="text/javascript">
  window.onmessage = (event) => {
    if (event.data) {
       let receivedData = event.data;
    }
  };
  
  //...
  
</script>

That means receivedData ="https://datastudio.google.com/embed/reporting/fkfkfkfkfffkkf/page/gurVC"

But now how can I put this variable into the iframe source? I tried to do it like this src=receivedData but it doesn't work.

<!DOCTYPE HTML>
<html lang="en-US">
<head>
    <meta charset="UTF-8">
    <link rel="mask-icon" href="https://assets-cdn.github.com/pinned-octocat.svg" color="#000000">
    <link rel="icon" type="image/x-icon" href="https://assets-cdn.github.com/favicon.ico">
    <link rel="shortcut icon" type="image/x-icon" href="https://assets-cdn.github.com/favicon.ico">
      
    <style> 
        body { background: #232323; width: 95%; margin: 0 auto; }
        
        /* Responsive Container for iFrame */
        .embed-container { position: relative; padding-bottom: 56.25%; height: 0; overflow: hidden; max-width: 100%; } 
        .embed-container iframe, .embed-container object, .embed-container embed { position: absolute; top: 0; left: 0; width: 100%; height: 100%; }
    </style>
    
    <title>Tech Ops PH | your &lt; IT / design &lt; partner </title>
  
  <script type="text/javascript">
  window.onmessage = (event) => {
    if (event.data) {
       let receivedData = event.data;
    }
  };
  
  //...
  
</script>
  
</head>

    <body>
        <div class='embed-container embed-responsive embed-responsive-4by3'>
                <iframe width="600" height="9000" src=receivedData frameborder="0" style="border:0" allowfullscreen></iframe>
        </div>
    </body>
    
    </html>

Solution

You could fill the iframe src property with javascript. Get the iframe by ID and fill the src property with your data.

<script type="text/javascript">
  window.onmessage = (event) => {
    if (event.data == true && event.data != "") {
      document.getElementById("myIframe").src = event.data; 
    }
  };
</script>

<div class='embed-container embed-responsive embed-responsive-4by3'>
  <iframe id="myIframe" width="600" height="9000" src=receivedData frameborder="0" style="border:0" allowfullscreen></iframe>
</div>

This should fill the src property on the iframe as soon as you receive data.

For a reference check this out w3schools iframe src property