JS实现简单计算器

JS实现简单计算器

这里写图片描述
HTML部分



<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Documenttitle>
head>
<body>
    <input type="text" id="txt1">
    <select name="" id="sel">
        <option value="+">+option>
        <option value="-">-option>
        <option value="*">*option>
        <option value="/">/option>
    select>
    <input type="text" id="txt2">
    <input type="button" value="=" id="btn">
    <input type="text" id="txt3">
body>
html>

JS部分

<script>
    var obtn = document.getElementById("btn");
    obtn.onclick=function(){
        var otxt1 =parseInt(document.getElementById("txt1").value);
        var otxt2 =parseInt(document.getElementById("txt2").value);
        var osel = document.getElementById("sel");
        var otxt3 = document.getElementById("txt3");
        var result;
        switch(osel.value){
            case "+":
            result = otxt1+otxt2;
            break;
            case "-":
            result = otxt1-otxt2;
            break;
            case "*":
            result = otxt1*otxt2;
            break;
            case "/":
            result = (otxt1/otxt2).toFixed(3);
        }
        otxt3.value=result;
    }
script>

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