尝试在if陈述中的输入字段中使用数字时获取NaN [英] Getting NaN when trying to use a number from an input field in an if statment

问题描述

我的部分反思有问题。我试图获取表格单元格以显示需要充电之前还剩下多少英里。

I am having a problem with part of my reflection. I am trying to get table cell to show how many miles are left until charging the car is needed.

我有一个输入单元格，用户可以在其中输入剩余的里程数（50）然后进行计算（50-（10％缓冲区，25）= 25，并显示在它旁边的单元格上。

I have an input cell where the user would type how many miles are left (50) and then a calculation happens (50 - (10% buffer, 25) = 25 and displays on the cell next to it.

我已经遍历了这里可以找到并尝试过的问题

I have gone through the questions on here I can find and tried the approaches others have tried but I really am at a dead end now.

JSFiddle在这里： https://jsfiddle.net/Coxy/gr5bcnsq/

The JSFiddle is here : https://jsfiddle.net/Coxy/gr5bcnsq/

代码为

var car_1_mtnc = document.getElementById('car-1-mtnc');
$(".confirm").click(function() {
var a =  parseInt(document.getElementById('car-1-cmra').value, 10);
var miles = a - 25;  

if ( a != Number ) {
    car_1_mtnc.textContent = "Please enter the miles left";
} else {
    car_1_mtnc.textContent = miles;
}
});

HTML

                                    <td><span id="car-1-cmra" class="answer" type="number"></span><input id="car-1-cmr" class="cmr" type="text" value="" placeholder="Enter Miles Left"></input></td>
                                    <td id="car-1-mtnc" class="mtnc"></td>

任何指针都会非常感谢，谢谢您的时间。

Any pointers would be really appreciated, thank you for your time.

推荐答案

您的代码有两个问题。

第一个问题是您得到了 .value ＃car-1-crma 的code>使用

The first is that you're getting .value from #car-1-crma using

document.getElementById('car-1-cmra').value

但这就是换出 span 因此没有.value-您可以在跨度上使用 .textContent 或使用（now-）隐藏输入

but that's the swap-out span so doesn't have a .value - you can either use .textContent on the span or use the (now-)hidden input

document.getElementById('car-1-cmr').value
document.getElementById('car-1-cmra').textContent
$("#car-1-cmra").text()

第二个是您正在使用

if (a != Number)

要在注释中提及，要检查输入是否为数字，请使用

as alluded to in the comments, to check if an input is a number or not, you use

if (isNaN(a))

进行这两个更改可以解决您的麻烦。英里范围计算： https://jsfiddle.net/4m8pa9dh （输入值）和 https://jsfiddle.net/4m8pa9dh/1/ （span textContent）

Making those two changes fixes your fiddle for the miles range calculation: https://jsfiddle.net/4m8pa9dh (input value) and https://jsfiddle.net/4m8pa9dh/1/ (span textContent)

这篇关于尝试在if陈述中的输入字段中使用数字时获取NaN的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！