calc object that runs in the terminal

terminalcalc.js

var calc = {
	
	lastResult: 0000,
	
	operate: function(operation, arg1, arg2) {
		switch(operation){
         case "add":
          if(arg2){
				calc.lastResult = calc.add(arg1, arg2);
				return this.lastResult;
			}else{
				calc.lastResult = calc.add(arg1, this.lastResult);
				return this.lastResult;
			}
			break;
		        case "subtract":
		         if(arg2){
				calc.lastResult = calc.subtract(arg1, arg2);
				return this.lastResult;
			}else{
				calc.lastResult = calc.subtract(arg1, this.lastResult);
				return this.lastResult;
			}
			break;
		        case "multiply":
		         if(arg2){
				calc.lastResult = calc.multiply(arg1, arg2);
				return this.lastResult;
			}else{
				calc.lastResult = calc.multiply(arg1, this.lastResult);
				return this.lastResult;
			}
			break; 
		        case "divide":
		         if(arg2){
				calc.lastResult = calc.divide(arg1, arg2);
				return this.lastResult;
			}else{
				calc.lastResult = calc.divide(arg1, this.lastResult);
				return this.lastResult;
			}
			break;

		}
	
	},
		add: function(arg1, arg2) {
		return arg1 + arg2;
	},
		subtract:function(arg1, arg2) {
		return arg1 - arg2;
	},
		multiply:function(arg1, arg2) {
		return arg1 * arg2;
	},
		divide:function(arg1, arg2) {
			if(arg2===0||arg1===0){return 0}
				else{return arg1 / arg2;}
	}
};

calc.clear = function() {
	this.operate('multiply', 0);
}

var operation = process.argv[2];
var a = parseInt(process.argv[3]);
var b = parseInt(process.argv[4]);

console.log(calc.operate(operation, a, b))