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if-else if与switch的练习1：输入两个数，输出两个数的加减乘除的值

news 2025/6/21 7:38:45

1.if-else if的练习

<!DOCTYPE html>
<html lang="en"><head><meta charset="UTF-8"><meta http-equiv="X-UA-Compatible" content="IE=edge"><meta name="viewport" content="width=device-width, initial-scale=1.0"><title>if-else if与switch的练习</title>
</head><body><input type="text" placeholder="请输入第1个数" id="txt1"><select name="" id="select"><option value="+">+</option><option value="-">-</option><option value="*">*</option><option value="/">/</option></select><input type="text" placeholder="请输入第2个数" id="txt2"><button id="btn">计算</button><input type="text" value="0.00" id="box">
</body>
<script>// 获取5个页面元素var txt1 = document.getElementById("txt1");var txt2 = document.getElementById("txt2");var select = document.getElementById("select")var btn = document.getElementById("btn");var box = document.getElementById("box");//按钮的点击事件btn.onclick = function () {// 获取文本框的value值var x = Number(txt1.value);var y = Number(txt2.value);var op = select.value; // 获取下拉列表的value值if (op == "+") {var s = (x + y).toFixed(2);} else if (op == "-") {var s = (x - y).toFixed(2);} else if (op == "*") {var s = (x * y).toFixed(2);} else {var s = (x / y).toFixed(2);}box.value = s; // 设置第三个文本框的value值}</script></html>

2.switch的练习

<!DOCTYPE html>
<html lang="en"><head><meta charset="UTF-8"><meta http-equiv="X-UA-Compatible" content="IE=edge"><meta name="viewport" content="width=device-width, initial-scale=1.0"><title>if-else if与switch的练习</title>
</head><body><input type="text" placeholder="请输入第1个数" id="txt1"><select name="" id="select"><option value="+">+</option><option value="-">-</option><option value="*">*</option><option value="/">/</option></select><input type="text" placeholder="请输入第2个数" id="txt2"><button id="btn">计算</button><input type="text" value="0.00" id="box">
</body>
<script>// 获取5个页面元素var txt1 = document.getElementById("txt1");var txt2 = document.getElementById("txt2");var select = document.getElementById("select")var btn = document.getElementById("btn");var box = document.getElementById("box");//按钮的点击事件btn.onclick = function () {// 获取文本框的value值var x = Number(txt1.value);var y = Number(txt2.value);var op = select.value; // 获取下拉列表的value值switch (op) {case "+":var s = x + y;break;case "-":var s = x - y;break;case "*":var s = x * y;break;case "/":var s = x / y;break;default:console.log("输入有误....");}s = s.toFixed(2)box.value = s;}
</script></html>