window.onload = function () {
var buttons = document.getElementsByTagName('span'),
result = document.querySelectorAll('.result p')[0],
clear = document.getElementsByClassName('clear')[0];
for (var i = 0; i < buttons.length; i++) {
if (buttons[i].innerHTML === '=') {
buttons[i].addEventListener("click", calculate(i));
} else {
buttons[i].addEventListener("click", addValue(i));
}
}
clear.onclick = function () {
result.innerHTML = '';
};
function addValue(i) {
return function () {
result.innerHTML += buttons[i].innerHTML;
};
}
function calculate(i) {
return function () {
var final_res = result.innerHTML;
result.innerHTML = eval(final_res);
};
}
};
