CF Calculator

calculator.js

var calcStr = ""; 	// computation String as such - to be eval()uated at the end.
var calcDec = false;	// toggle for checking if decimal point is set
var calcDone = false;	// toggle for checking eval()

var operand = [];	// collecting operands	-> dataGathering()
var numbers = [];	// collecting numbers	-> dataGathering()

function dataGathering(a){
	if (calcStr) {
		numbers.push(parseFloat(calcStr));
		operand.push(a);
		calcStr = "";
		calcDec = false;
	}
}

var myMath = {
	"round": function(number, precision) {
		var factor = Math.pow(10, precision);
		return Math.round(number * factor)/factor;
	}
};

function calculate(){
	var evt = event.target.id;

	switch(evt){
		case "reset":
			calcStr = "";
			operand = [];
			numbers = [];
			break;
		case "divide":
			dataGathering("/");
			break;
		case "multiply":
			dataGathering("*");
			break;
		case "add":
			dataGathering("+");
			break;
		case "substr":
			dataGathering("-");
			break;
		case "equals":
			if(numbers.length > 0){
				var calcTemp = calcStr;
				calcStr = "";
				while(numbers.length > 0){
					calcStr += numbers.shift() + operand.shift();
				}
				calcStr += calcTemp;
				calcStr = myMath.round(eval(calcStr),5);
				calcDone = true;
				/*
				* attempt to change the display to exponential
				* when exceeding screen's limit.
				*	Not yet functioning. Figure out later.
				var digitCount = (calcStr + '').replace('.', '').length;
				if (digitCount > 7) calcStr.toExponential();
				*/
			}
			break;
		case "decimal":
			if (calcStr && !calcDec) calcDec = true;
			break;
		default:
			if (evt.match(/\d/)){
				if(calcDone) {
					calcStr = "";
					calcDone = false;
				}
				if (calcDec) {
					calcStr += ".";
					calcDec = false;
				}
				calcStr += evt;
			}
			break;
	}
	if (numbers.length > 0 && !calcStr) document.getElementById("display").textContent = numbers[numbers.length-1];
	else document.getElementById("display").textContent = calcStr;
}

document.getElementById("calculator").addEventListener("click", calculate);