Xemectrum

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function validate() {
	var ic = document.form.textfield.value;
	if (ic.length != 9) { 
		//alert("Please enter the IC number in the format:\n   SXXXXXXXA");
		document.form.textfield.focus();
		return;
		//return false;
	}
	
	var icArray = new Array(9);
	for(i = 0; i < 9; i++) {
		icArray[i] = ic.charAt(i);
	}
	
	icArray[1] *= 2;
	icArray[2] *= 7;
	icArray[3] *= 6;
	icArray[4] *= 5;
	icArray[5] *= 4;
	icArray[6] *= 3;
	icArray[7] *= 2;
	
	var weight = 0;
	for(i = 1; i < 8; i++) {
		weight += parseInt(icArray[i]);
	}
	
	var offset=(icArray[0]=="T"||icArray[0]=="G")?4:0;
	var temp=(offset+weight)%11;
	
	var st=Array("J","Z","I","H","G","F","E","D","C","B","A");
	var fg=Array("X","W","U","T","R","Q","P","N","M","L","K");
	
	var theAlpha;
	if     (icArray[0]=="S"||icArray[0]=="T") { theAlpha=st[temp]; }
	else if(icArray[0]=="F"||icArray[0]=="G") { theAlpha=fg[temp]; }
	
	if (icArray[8] != theAlpha) {
		document.getElementById("image").src="cross.gif";
		//alert("Bad IC Number: " + ic);
	}
	else {
		document.getElementById("image").src="tick.gif";
		//alert("Good IC Number: " + ic);
	}
}