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problem understanding window.onload event


HJohn
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Hi, I am new to javascript. I am trying to understand why something that seems so simple is not working for me. I created a simple page to learn javascript. However, I don't understand why it is not working. I included a reference to an external javascript file on the head tag of the html but I always get was getting an undefined error. My question, is the window.onload event fired before or after the html file is loaded? If I put the reference to the javascript file just before the close body tag, commented on the html, it works.

 

<!DOCTYPE html><html> <head> <script type="text/javascript" src="testjavascript.js"></script> </head> <body> <h1> <script type="text/javascript"> document.write("Inside javascript") </script> </h1> <h1>Below here should be the test.</h1> <h1 id = "test">test</h1> <button id = "cmdAlert">Click Here For An Alert Message</button> <!--<script type="text/javascript" src="testjavascript.js"></script>--> </body></html>

 

javascript file

 

window.onload = initall();

function initall(){ button = window.document.getElementById("cmdAlert"); if (button) { button.onClick = "cmdAlert_Click()"; } else { alert("Can not access button."); } }

 

function cmdAlert_Click() { alert("This is a javascript test.");}

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