How can I fix a "not a function" JavaScript error in Firefox's console?

The code below works fine in Chrome but does not work in Firefox. The error displayed in the Firefox console is "Error: document.forms.frmCreateNewEmployee.elements is not a function".

document.forms['frmCreateNewEmployee'].elements('employeeType').value = document.getElementById("userType").options[document.getElementById("userType").selectedIndex].value;

How can I resolve this error开发者_开发技巧?

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Change .elements('employeeType') to .elements['employeeType'] to fix the error.