即使输入为整数，JavaScript也会返回NaN [英] JavaScript returns NaN even if input is an integer

问题描述

我在输入框中输入一个整数，它仍然返回'NaN'.

I am typing an integer in the input box and it still returns 'NaN'.

function goldenFunctiona() {
  a = document.getElementById("sidea");
  parseInt(a, 10);
  b = ((a + a) * (Math.pow(5, 0.5))) / 2;
  document.getElementById("b").innerHTML = b;
}

<div id="top">
  <p>Side a =</p>
  <input id="sidea" type="number">
  <button id="button" onclick="goldenFunctiona()" type="button">Find side b</button>
  <p id="b"></p>
</div>

我不知道出了什么问题，但这可能真的很简单.预先感谢.

I don't know what's going wrong but it's probably something really simple. Thanks in advance.

推荐答案

document.getElementById("sidea")不返回 number ，但返回元素.使用 document.getElementById("sidea").value 来获取元素值.

document.getElementById("sidea") doesn't returns a number, but an element. Use document.getElementById("sidea").value instead to get the element value.

所以:

function goldenFunctiona() {
    var sideaVal = document.getElementById("sidea").value;

    var a = parseInt(sideaVal , 10); // Get parseInt's return value or 'a' will still be a string
    var b = ((a + a) * (Math.pow(5, 0.5))) / 2;

    document.getElementById("b").innerHTML = b;
}

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