Calculator

If somebody ever asked me, "what's the dorkiest piece of code you've ever written," this calculator would be near the top. I can't believe I even spent an hour on this (90 percent of which was making those cute little buttons).

The script

var displayvalue = "";	// what is shown in the display window of the calculator
var equation = "";	// the running equation to be calculated
var newdisplay = true;	// we're done with the value in the window and are ready for a new number

	
// sets the value displayed on the calculator
function setDisplayValue(newval) {

	// if we're done with the screen value, we'll overwrite it with a blank
	if (newdisplay) {
		displayvalue="";
	}

	// concatenate the new number onto the display value
	displayvalue += newval;
	document.calculator.currval.value = displayvalue;

	// so far, we're pretty sure we will want the next entry to be concatenated
	newdisplay = false;
}
	
// evaluate the equation
function equals() {
	// add the current displayvalue to the string
	equation += displayvalue;

	// evaluate & display
	displayvalue = eval (equation);
	document.calculator.currval.value = displayvalue;

	// reset
	equation = "";
	newdisplay = true;
}
	
// concatenate a value and an operator onto the equation
function operator(opr) {
	// concatenate the value
	equation += displayvalue;

	// display the current running total	
	displayvalue = eval(equation);
	document.calculator.currval.value = displayvalue;

	// concatenate the operator
	equation += opr;

	// reset the newdisplay value
	newdisplay = true;
}