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| import React, { useReducer } from "react";
import DigitButton from "./DigitButton";
import OperationButton from "./OperationButton";
import "./style.css";
export const ACTIONS = {
ADD_DIGIT: "add-digit",
CHOOSE_OPERATION: "choose-operation",
CLEAR: "clear",
EVALUATE: "evaluate",
PERCENTAGE: "percentage",
NEGATE: "negate",
};
function reducer(state, { type, payload }) {
switch (type) {
case ACTIONS.ADD_DIGIT:
if (state.overwrite) {
return { ...state, currentOperand: payload.digit, overwrite: false };
}
if (payload.digit === "0" && state.currentOperand === "0") return state;
if (payload.digit === "." && state.currentOperand.includes("."))
return state;
return {
...state,
currentOperand: `${state.currentOperand || ""}${payload.digit}`,
};
case ACTIONS.CHOOSE_OPERATION:
if (state.currentOperand == null && state.previousOperand == null)
return state;
if (state.currentOperand == null) {
return { ...state, operation: payload.operation };
}
if (state.previousOperand == null) {
return {
...state,
operation: payload.operation,
previousOperand: state.currentOperand,
currentOperand: null,
};
}
return {
...state,
previousOperand: evaluate(state),
operation: payload.operation,
currentOperand: null,
};
case ACTIONS.CLEAR:
return initialState;
case ACTIONS.EVALUATE:
if (!state.operation || !state.currentOperand || !state.previousOperand) {
return state;
}
return {
...state,
overwrite: true,
previousOperand: null,
operation: null,
currentOperand: evaluate(state),
};
case ACTIONS.PERCENTAGE:
if (state.currentOperand == null) return state;
return {
...state,
currentOperand: (parseFloat(state.currentOperand) / 100).toString(),
};
case ACTIONS.NEGATE:
if (state.currentOperand == null) return state;
return {
...state,
currentOperand: (parseFloat(state.currentOperand) * -1).toString(),
};
default:
return state;
}
}
function evaluate({ currentOperand, previousOperand, operation }) {
const prev = parseFloat(previousOperand);
const current = parseFloat(currentOperand);
if (isNaN(prev) || isNaN(current)) return "";
let computation = "";
switch (operation) {
case "+":
computation = prev + current;
break;
case "-":
computation = prev - current;
break;
case "*":
computation = prev * current;
break;
case "/":
computation = prev / current;
break;
default:
return "";
}
return computation.toString();
}
const initialState = {
currentOperand: "0",
previousOperand: null,
operation: null,
};
const App = () => {
const [{ currentOperand, previousOperand, operation }, dispatch] = useReducer(
reducer,
initialState
);
return (
<div className="calculator-grid">
<div className="output">
<div className="previous-operand">
{previousOperand} {operation}
</div>
<div className="current-operand">{currentOperand}</div>
</div>
</div>
);
};
export default App;
|
