How Do I Successfully Trigger a JavaScript Function with an HTML Button?

Calling a JavaScript Function with an HTML Button

Issue

In an attempt to trigger a JavaScript function, an HTML button has been employed. However, the intended functionality is not achieved.

Resolution

Utilizing an HTML button to invoke a JavaScript function can be accomplished in several ways:

1. HTML Event Definition:

   <input>

2. DOM Event Property Assignment:

   // Using a function pointer:
   document.getElementById("clickMe").onclick = doFunction;
   
   // Using an anonymous function:
   document.getElementById("clickMe").onclick = function () { alert('hello!'); };

3. Event Handler Function Attachment:

   var el = document.getElementById("clickMe");
   if (el.addEventListener)
       el.addEventListener("click", doFunction, false);
   else if (el.attachEvent)
       el.attachEvent('onclick', doFunction);

The first and second methods are mutually exclusive. The third method allows for multiple functions to be attached to the same event handler.

Troubleshooting

It is likely that the issue lies in the CapacityChart() function. Revisiting the code example reveals two popups opening. To debug:

1. Replace:

   CapacityWindow.document.write(s);

   with:

   CapacityWindow.document.open("text/html");
   CapacityWindow.document.write(s);
   CapacityWindow.document.close();

2. Replace references to document.all with document.getElementById.

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