javascript 收到 NaN 错误，不知道为什么
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Getting a NaN error, can't figure out why
提问by notknown7777
I have this code in JavaScript:
我在 JavaScript 中有这个代码：
SolarPanels = parseInt(lRemainingWidth / (panel_width + ( 2 * lPanelInterSpace)));
and then I alert the SolarPanelsvalue which gives NaNas output,
然后我提醒作为输出SolarPanels给出的值NaN，
alert("SolarPanels "+SolarPanels);
This 1 line is a tiny part of a huge calculation, but my code seems to fail here,
with the use of alerts i've read out the values of SolarPanels, lRemainingWidth, panel_widthand lPanelInterSpacewhich are the following:
这1线是一个巨大的计算的一小部分，但我的代码似乎在这里失败，使用警报的我已经读出的值SolarPanels，lRemainingWidth，panel_width和lPanelInterSpace它有以下几种：
lRemainingwidth = 17.4.320227272727276
SolarPanels = 0
panel_width = 1.65
lPanelInterSpace = 0.02
I think it has to do with the 2 dots in lRemainingWidth, either way, I don't know how to fix it. Why the lRemainingWidthhas 2 dots?
我认为这与 中的 2 个点有关lRemainingWidth，无论哪种方式，我都不知道如何解决。为什么lRemainingWidth有2个点？
Update :
更新 ：
This is the part that calculates the lRemainingWidth :
这是计算 lRemainingWidth 的部分：
if(HalforDouble === "Yes")
{
lRemainingWidth = (roof_ridge /2) + ((lRemainingHeight / Math.tan((lRoofEdgeDegrees * Math.PI) / 180)) - lRoofEdge);
}
else
{
lRemainingWidth = roof_ridge + (2 * ((lRemainingHeight / Math.tan((lRoofEdgeDegrees * Math.PI) / 180)) - lRoofEdge));
}
The values here are:
这里的值是：
lRemainingWidth = 0
roof_ridge = 17
lRemainingHeight = 20.769000000000002
lRoofEdgeDegrees = 83.5169263071276
lRoofEdge = 0.2
回答by Denys Séguret
Your problem is that you mix strings and numbers
你的问题是你混合了字符串和数字
Start with this code before any computation :
在任何计算之前从以下代码开始：
var roof_ridge = parseFloat(roof_ridge);
There might be other strings hidden in your code but we don't see them. Apply the same conversion on them.
您的代码中可能隐藏了其他字符串，但我们看不到它们。对它们应用相同的转换。
回答by Mike Samuel
lRemainingWidth = roof_ridge + (2 * ((lRemainingHeight / Math.tan((lRoofEdgeDegrees * Math.PI) / 180)) - lRoofEdge));
lRemainingWidth = roof_ridge + (2 * ((lRemainingHeight / Math.tan((lRoofEdgeDegrees * Math.PI) / 180)) - lRoofEdge));
If roof_ridgeis a string then the +does string concatenation instead of addition.
如果roof_ridge是字符串，则+执行字符串连接而不是加法。
Change this to
将此更改为
lRemainingWidth = +roof_ridge + (2 * ((lRemainingHeight / Math.tan((lRoofEdgeDegrees * Math.PI) / 180)) - lRoofEdge));
The prefix +operator in +roof_ridgecoerces its argument to a number.
前缀+运算符 in 将+roof_ridge其参数强制为数字。
回答by Sergii Stotskyi
It seems like a cornerstone of the issue in roof_ridgevariable. This variable is instance of String class, not a number. So, when you code go to this line:
这似乎是roof_ridge变量问题的基石。此变量是 String 类的实例，而不是数字。因此，当您编写代码时，请转到这一行：
lRemainingWidth = roof_ridge + (2 * ((lRemainingHeight / Math.tan((lRoofEdgeDegrees * Math.PI) / 180)) - lRoofEdge));
the next calculation is done:
下一个计算完成：
'17' + whatever_float_value = got string concatenation instead of number's sum.
To fix this just add:
要解决这个问题，只需添加：
lRemainingWidth = parseFloat(roof_ridge) + (2 * ((lRemainingHeight / Math.tan((lRoofEdgeDegrees * Math.PI) / 180)) - lRoofEdge));
