javascript 中的计算错误 未知的输出"NaN"

Question

一切都对我有好处，但结果总是出现 Nan

这是代码

.js

function myFunction() {
var x = document.getElementById("myInput").value;
var str1 = document.getElementById("demo");
var str2 = document.getElementById("demo2");
var str3 = document.getElementById("demo3");
var str4 = x * str2;
document.getElementById("demo").innerHTML = str4 * str3;

目录

<p id="demo"></p>
<br>
<p id="demo2">1</p>
<br>
<p id="demo3">1</p>

输出：楠

Answer 1

function myFunction() {
var x = document.getElementById("myInput").value;
var str1 = document.getElementById("demo").innerText;
var str2 = document.getElementById("demo2").innerText;
var str3 = document.getElementById("demo3").innerText;
var str4 = parseInt(x) * parseInt(str2);
document.getElementById("demo").innerHTML = (parseInt(str4) * parseInt(str3)).toString();
}

<p id="demo"></p>
<br>
<p id="demo2">2</p>
<br>
<p id="demo3">10</p>
<input placeholder="enter" id="myInput" type="number" required/>
<input type="button" onClick="myFunction()" value="Calculate"/>