b 用js编写calc函数获取并转换输入的数据判断不合法给出提示调用指定函数完成相关计算

function calc() { var num1 = parseFloat(document.getElementById("num1").value); var num2 = parseFloat(document.getElementById("num2").value); var operator = document.getElementById("operator").value;

if (isNaN(num1) || isNaN(num2)) { alert("请输入数字"); return; }

switch (operator) { case "+": document.getElementById("result").value = add(num1, num2); break; case "-": document.getElementById("result").value = subtract(num1, num2); break; case "*": document.getElementById("result").value = multiply(num1, num2); break; case "/": if (num2 === 0) { alert("除数不能为0"); return; } document.getElementById("result").value = divide(num1, num2); break; default: alert("请选择运算符"); break; } }

function add(num1, num2) { return num1 + num2; }

function subtract(num1, num2) { return num1 - num2; }

function multiply(num1, num2) { return num1 * num2; }

function divide(num1, num2) { return num1 / num2;