function checkForm() {
	if (document.forms[0].naam.value == "") {
		alert("Vul uw naam in")
		document.forms[0].naam.focus()
	} else if (document.forms[0].straat.value == "") {
		alert("Vul uw straat in")
		document.forms[0].straat.focus()
	} else if (document.forms[0].tel.value == "") {
		alert("Vul uw telefoonnummer in")
		document.forms[0].tel.focus()
	} else if (!isTelNummer(document.forms[0].tel.value)) {
		alert("Het door u ingevulde telefoonummer is onjuist")
		document.forms[0].tel.focus()
		document.forms[0].tel.value = ''
	} else if (document.forms[0].mail.value == "") {
		alert("Vul uw e-mailadres in")
		document.forms[0].mail.focus()
	} else if (!checkEmail(document.forms[0].mail.value)) {
		alert("Het is door u ingevulde e-mailadres in onjuist")
		document.forms[0].mail.focus()
		document.forms[0].mail.value = ''
	} else if (document.forms[0].codeI.value == "")	{
		alert("Geef een code op.")
		document.forms[0].codeI.focus()
	} else
		document.forms[0].submit()
}

function isTelNummer(str) {
    if(!str)
        return false

    for(var i = 0;i < str.length;i++) {
        var ch = str.charAt(i)

        if ("0123456789-() +".indexOf(ch) == -1)
            return false
    }

    return true
}

function checkEmail(strEmail) {
	strtmpEmail = String(strEmail)

	if (strtmpEmail.indexOf("@") == -1 || strtmpEmail.indexOf(".") == -1)
		return false

	nAt = strtmpEmail.indexOf("@")

	if (nAt > 0) {
		strCheck = strtmpEmail.slice(nAt + 1)

		if (strCheck.indexOf(".") <= 0)
			return false
		else
			return ((parseInt(strCheck.length) -1) - parseInt(strCheck.indexOf("."))  > 1)
	} else
		return false
}