在 Javascript 中，简单的计算器，不起作用

Question

我试图通过 prompt() 和动作名称来获取数字。但结果并不如预期

我是编程新手.. 代码：

function add(n1, n2){   return n1 + n2;}

function sub(n1, n2){   return n1 - n2;}

function mult(n1, n2){  return n1 * n2;}

function div(n1, n2){   return n1/n2;}

function calculator(n1, n2, action){

    alert(action(n1, n2));

}

calculator(prompt("first no,"), prompt("second No"), prompt("calc"));

Answer 1

你需要做两件事：将输入解析为浮点数映射用户给定的函数名function add(n1, n2) { return n1 + n2; }function sub(n1, n2) { return n1 - n2; }function mult(n1, n2) { return n1 * n2; }function div(n1, n2) { return n1 / n2; }function calculator(n1, n2, action) {  alert(action(n1, n2));}function findOperation(name) {  switch (name) {    case "sub":      return sub;    case "mult":      return mult;    case "div":      return div;    case "add":    default:      return add;  }}calculator(  parseFloat(prompt("first no,")),  parseFloat(prompt("second No")),  findOperation(prompt("Operation Name?")));

Answer 2

我建议您花时间学习一些基础知识，除非您像这样使用 eval() ，否则您无法将字符串转换为函数调用：function add(n1, n2){ return n1 + n2;}function sub(n1, n2){ return n1 - n2;}function mult(n1, n2){ return n1 * n2;}function div(n1, n2){ return n1/n2;}function calculator(n1, n2, action){alert(eval(`${action}(${n1}, ${n2})`));}calculator(prompt("first no,"), prompt("second No"), prompt("calc"));但这确实是 hacky 和不安全的代码，更好的方法是：const ops = {"add": (n1, n2) => n1 + n2,"sub": (n1, n2) => n1 - n2,"mult": (n1, n2) => n1 * n2,"div": (n1, n2) => n1/n2}function calculator(n1, n2, action){alert(ops[action](parseFloat(n1), parseFloat(n2)));}calculator(prompt("first no,"), prompt("second No"), prompt("calc"));还要注意 parseFloat()，如果你将参数保存为字符串，你会得到：input: "1", "2", "add" output: "12"

Answer 3

计算器功能应该是：function calculator(n1, n2, action){    alert(eval(action+'('+n1+', '+n2+')'));}