JavaScript 中的計算器有重置按鈕問題

Question

我的任務是做一個計算 2 個數字的計算器，並為加分一個重置按鈕，但我很困惑，因為我無法讓它正常工作

 let n1 = document.getElementById("num1").innerText = Number(prompt("N1")) let n2 = document.getElementById("num2").innerText = Number(prompt("N2")) let changeR = document.getElementById("result") function add(){ let sum = n1 + n2 changeR.innerText = sum } function sub(){ let sum = n1 - n2 changeR.innerText = sum } function mult(){ let sum = n1 * n2 changeR.innerText = sum } function divi(){ let sum = n1 / n2 changeR.innerText = sum } function rest() { let sum = 0 console.log(sum) changeR.innerText = sum let n1 = document.getElementById("num1").innerText = Number(prompt("N1")) let n2 = document.getElementById("num2").innerText = Number(prompt("N2")) }

 <h1>Numbers</h1> <p id="num1"></p> <p id="num2"></p> <hr> <h1>Result:<span id="result"></h1> <hr> <button onclick="add()">+</button> <button onclick="sub()">-</button> <button onclick="mult()">*</button> <button onclick="divi()">/</button> <button onclick="rest()">reset</button>

所以我試圖解決我的問題，但我不能，當我按重置以某種方式重置結果時，值仍然存在並且無法計算新數字

Answer 1

很簡單，你需要做的就是讓變量是全局的。

The issue you were facing was that each function had its own variable for sum ( they were defined again with let and thus existed in the scope of the function sperate from their global counterpart ) and hence each function was only accessing its own variable and in the重置 function 的情況下也有自己的 n1 和 n2 填充了提示中的最新值，但全局 n1 和 n2 值沒有更改，因為其他函數使用全局 n1 和 n2 來計算舊的結果結果顯示給他們，而重置每次都在自己的 n1 和 n2 中設置值，而不會影響全局 n1 和 n2。

希望能幫助到你，

let n1 = document.getElementById("num1").innerText = Number(prompt("N1"))
let n2 = document.getElementById("num2").innerText = Number(prompt("N2"))
let changeR = document.getElementById("result")
let sum = 0;

function add(){
sum = n1 + n2
changeR.innerText = sum
}


function sub(){
sum = n1 - n2
changeR.innerText = sum
}

function mult(){
sum = n1 * n2
changeR.innerText = sum
}

function divi(){
sum = n1 / n2
changeR.innerText = sum
}

function rest(){

sum = 0;
console.log(sum)
changeR.innerText = sum
n1 = document.getElementById("num1").innerText = Number(prompt("N1"))
n2 = document.getElementById("num2").innerText = Number(prompt("N2"))
}