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calc.js
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calc.js
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const screen = document.querySelector(".screen-inner");
let buffer = "";
let runningTotal = 0;
let previousOperator;
function buttonClick(value) {
if (isNaN(parseInt(value))) {
handleOperator(value);
} else {
handleNumber(value);
}
rerender();
}
function handleNumber(number) {
if (buffer === "0") {
buffer = number;
} else {
buffer += number;
}
}
function handleMath(operator) {
if (buffer === "0") {
// Do nothing already 0
return;
}
const intBuffer = parseInt(buffer);
if (runningTotal === 0) {
runningTotal = intBuffer;
} else {
flushOperation(intBuffer);
}
previousOperator = operator;
buffer = "0";
}
function flushOperation(intBuffer) {
switch (previousOperator) {
case "+":
runningTotal += intBuffer;
break;
case "-":
runningTotal -= intBuffer;
break;
case "x":
runningTotal *= intBuffer;
break;
case "÷":
runningTotal /= intBuffer;
break;
default:
console.error("Error - hit default case in flushOperation");
break;
}
}
function handleOperator(operator) {
switch (operator) {
case "Clear":
buffer = "0";
runningTotal = 0;
previousOperator = null;
rerender();
break;
case "=":
if (previousOperator === null) {
// need two numbers to do math
return;
}
flushOperation(parseInt(buffer));
previousOperator = null;
buffer = "" + runningTotal;
runningTotal = 0;
break;
case "←":
if (buffer.length === 1) {
buffer = "0";
} else {
buffer = buffer.substring(0, buffer.length - 1);
}
break;
case "+":
handleMath(operator);
break;
case "-":
handleMath(operator);
break;
case "x":
handleMath(operator);
break;
case "÷":
handleMath(operator);
break;
default:
console.error("Error - hit default case in handleOperator");
break;
}
}
function rerender() {
screen.innerText = buffer;
}
function init() {
document.querySelector(".components").addEventListener("click", (event) => {
buttonClick(event.target.innerText);
});
}
init();