数学运算

Question

我是初学者，这是我第一次在这里写作。所以我的目标是制作一个强大的计算器，现在我发现自己在计算过程中遇到更改操作的问题 - 例如：我得到 1+1 但当我处于 1+ 并想将其更改为-,/ 或 * 我不能。试图找到解决方案，但其他人以自己的方式进行计算，所以我在这里问。起草你的问题是建议显示最少的代码，所以我 post 我认为下面是相关的。如果有人需要更多代码来帮助我解决这个问题，我可以发送代码笔 link 但建议不要发送到这里。

class Calculator {
    constructor(previousOperandTextElement, currentOperandTextElement){
        this.previousOperandTextElement = previousOperandTextElement;
        this.currentOperandTextElement = currentOperandTextElement;
        this.readyToReset = false;
        this.clear();
    }

    clear() {
        this.currentOperand = "";
        this.previousOperand = "";
        this.operation = undefined;

    }

    delete() {
        this.currentOperand = this.currentOperand.toString().slice(0, -1);
    }

    appendNumber(number) {
        if (number === "." && this.currentOperand.includes(".")) return
        this.currentOperand = this.currentOperand.toString() + number.toString();
    }

    chooseOperation(operation) {
        if (this.currentOperand === "") return
        if (this.currentOperand !== "" && this.previousOperand !== "") this.compute();
        this.operation = operation;
        this.previousOperand = this.currentOperand;
        this.currentOperand = "";
    }

    compute() {
        let computation
        const prev = parseFloat(this.previousOperand);
        const current = parseFloat(this.currentOperand);
        if (isNaN(prev) || isNaN(current)) return;
        switch (this.operation)  {

        case "+":
            computation = prev + current;
        break;

        case "-":
            computation = prev - current;
        break;

        case "*":
            computation = prev * current;
        break;

        case "÷":
            computation = prev / current;
        break;
        default:
        return;
    
        }
        this.readyToReset = true;
        this.currentOperand = computation;
        this.operation = undefined;
        this.previousOperand = "";
    }

    updateDisplay() {
        this.currentOperandTextElement.innerText = this.currentOperand;
        if (this.operation != null) {
            this.previousOperandTextElement.innerText =
            `${this.previousOperand} ${this.operation}`
        } else {
            this.previousOperandTextElement.innerText = "";
        }

    }
}


const numberButtons = document.querySelectorAll("[data-number]");
const operationButtons = document.querySelectorAll("[data-operation]");
const equalsButton = document.querySelector("[data-equals]");
const deleteButton = document.querySelector("[data-delete]");
const allClearButton = document.querySelector("[data-clear]");
const previousOperandTextElement = document.querySelector("[data-previous-operand]");
const currentOperandTextElement = document.querySelector("[data-current-operand]");

const calculator = new Calculator(previousOperandTextElement,
    currentOperandTextElement);

allClearButton.addEventListener("click", () => {
    calculator.clear();
    calculator.updateDisplay();
})

numberButtons.forEach(button => {
    button.addEventListener("click", () => {

        if(calculator.previousOperand === "" &&
        calculator.currentOperand !== "" &&
    calculator.readyToReset) {
            calculator.currentOperand = "";
            calculator.readyToReset = false;
        }
        calculator.appendNumber(button.innerText)
        calculator.updateDisplay();
    })
})

operationButtons.forEach(button => {
    button.addEventListener("click", () => {
        calculator.chooseOperation(button.innerText)
        calculator.updateDisplay();
    })
})

equalsButton.addEventListener("click", button => {
    calculator.compute();
    calculator.updateDisplay();
})

deleteButton.addEventListener("click", button => {
    calculator.delete();
    calculator.updateDisplay();
})

.calculator-grid{
   display: grid;
   justify-content: center;
   align-items: center;
   min-height: 100;
   grid-template-columns: repeat(4, 80px);
}

.calculator-grid > button {
    cursor: pointer;
    font-size: 2em;
    border: 1px solid rgb(0, 0, 0);
    outline: none;
    background-color: rgb(233, 129, 129);
    margin: 1px;
    border-radius: 10px;
}

.output {
    grid-column: 1 / -1;
    background-color: rgb(251, 251, 251);
    display: flex;
    align-items: flex-end;
    justify-content: space-between;
    flex-direction: column;
    padding: 10px;
    height: 100px;
}

#kalkulacka{
 width: 360px;
 height: 520px;
 background-color: rgb(0, 255, 221);
 margin: auto;
 top: 20px;
 position: center;
 border-radius: 10px;
}

.span-two{
    grid-column: span 2;
}

<div id="kalkulacka" class="calculator-grid">
        <div class="output">
            <div data-history class="history">22</div>
            <div data-previous-operand class="previous-operand">22</div>
            <div data-current-operand class="current-operand">22</div>
        </div>
        <button data-clear>AC</button>
        <button data-delete>DEL</button>
        <button data-converse>+/-</button>
        <button data-operation>÷</button>
        <button data-number>7</button>
        <button data-number>8</button>
        <button data-number>9</button>
        <button data-operation>*</button>
        <button data-number>4</button>
        <button data-number>5</button>
        <button data-number>6</button>
        <button data-operation>-</button>
        <button data-number>1</button>
        <button data-number>2</button>
        <button data-number>3</button>
        <button data-operation>+</button>
        <button data-number>.</button>
        <button data-number>0</button>
        <button data-equals class="span-two">=</button>
    </div>

Answer 1

我想这就是你想要的。

在您的构造函数中，添加：

   this.lastEntryWasOperation = false;

在appendNumber()的开头，加上：

   this.lastEntryWasOperation = false;

然后将chooseOperation()改为：

if (this.lastEntryWasOperation)
    this.operation = operation;
else{
    if (this.currentOperand === "") return
    if (this.currentOperand !== "" && this.previousOperand !== "") this.compute();
    this.operation = operation;
    this.previousOperand = this.currentOperand;
    this.currentOperand = "";
}

this.lastEntryWasOperation = true;

因此我们跟踪最后按下的键是否是操作符，如果是操作符则将标志设置为 true，否则设置为 false。

然后，如果第二个运算符紧跟在另一个运算符之后，我们只需覆盖它而不是移动操作数。

数学运算

Math operations

javascript

calculator