Javascript Logic and data (originally one file)

Button logic.js

for(var i = 0; i < keys.length; i++) {
	keys[i].onclick = function(e) {
		// Get the input and button values
        var result = document.querySelector('#result');
		var input = document.querySelector('.screen');
		var inputVal = input.innerHTML;
        var id = '#' + this.getAttribute('id');
		var btnVal = this.innerHTML;
        console.log(btnVal);
		
		// Now, just append the key values (btnValue) to the input string and finally use javascript's eval function to get the result
		// If clear key is pressed, erase everything
        if (btnVal == 'C') {
			input.innerHTML = '';
		}
		
		// If eval key is pressed, calculate and display the result
		else if(btnVal == 'Calculate') {
			result.innerHTML = Math.floor(list_of_val.reduce(function(a, b) { return a + b; }, 0) / 175) + " Panel(s)!";
            
		}
		

		// Now only the decimal problem is left. We can solve it easily using a flag 'decimalAdded' which we'll set once the decimal is added and prevent more decimals to be added once it's set. It will be reset when an operator, eval or clear key is pressed.
		else if(btnVal == '.') {
			if(!decimalAdded) {
				input.innerHTML += data[inputVal];
				decimalAdded = true;
			}
		}
		
		// if any other key is pressed, just append it
		else {
            if (data[btnVal] == -1) {
                list_of_val.pop();
                str_sf.pop()
                
                input.innerHTML = str_sf.join(" + ");
                
            }
            else if (data[btnVal] != 0)  {
                console.log(data[btnVal]);
                list_of_val.push(data[btnVal]);
                str_sf.push(btnVal);
                console.log(list_of_val);
                console.log(str_sf);
                input.innerHTML = str_sf.join(" + ");
            }
		}
		
		// prevent page jumps
		e.preventDefault();
	} 
}

Database for devices.js

var data = {
    
    "del": -1,
    "Next": 0,
    "Back": 0,
    "Request Form": 0,
    
    "Lights": 0,
    "10 LED Bulb": 85,
    "30 LED Bulb": 255,
    "50 LED Bulb": 425,
    "10 Fluor. Bulb": 4250,
    "30 Fluor. Bulb": 12750,
    "50 Fluor. Bulb": 21250,
    
    
    "General": 0,
    "Plasma TV": 300,
    "(20in+) LED TV": 80,
    "(60in+) LED TV": 150,
    "(20in+) LCD TV": 120,
    "(60in+) LCD TV": 250,
    
    "Devices": 0,
    "Xbox 360": 120,
    "Xbox One": 90,
    "Play Station 3": 800,
    "Play Station 4": 90,
    "Wii U": 32.6,
    "Smart Phone": 0,
    
    
    "Computers": 0,
    "PC": 275,
    "Laptop PC": 75,
    "iMac": 230,
    "Laptop Mac": 205,
    "Printer": 25,
    "Router": 10,
    
    
    "Kitchen": 0,
    "Blender": 350,
    "Coffe Machine": 1100,
    "Oven": 350,
    "Microwave": 1150,
    "Dish Washer": 275,
    "Fridge / Freezer": 275,
    
    "Washroom": 0,
    "Electronic Razor": 17.5,
    "Blow Dryer": 2150,
    "Dryer": 2500,
    "Washer": 500,
    "Iron": 1000,
    
    
    "Home": 0,
    "A/C" :2500,
    "Fan": 50,
    "Water Pump": 00
    
    
};