新增负号

jsq.html

@@ -82,6 +82,7 @@
         <button onclick="compute()">=</button>
         <button onclick="chooseOperation('+')">+</button>
         <button onclick="chooseOperation('%')">%</button>
+        <button onclick="appendNumber('-')">±</button>
     </div>
 </div>
 
@@ -94,6 +95,7 @@
 
     function appendNumber(number) {
         if (number === '.' && currentOperand.includes('.')) return;
+        if (number === '-' && currentOperand.length > 0) return; // 防止在数字中间添加负号
         currentOperand += number;
         updateDisplay();
     }