Question

当我使用--l = 4和--w = 4运行solve-3时，函数rectangle.perimeter和rectangle.area输出NaN。为什么？对我来说，似乎输入的整数被转换为字符串，因此为什么我添加了Number（），但这并没有改变任何东西。

文件1：rect-2.js

module.exports = function(l,w,callback) {
try {
    if (l < 0 || w < 0) {
        throw new Error("Rectangle dimensions should be greater than zero: l = " + l + ", and w = " + w);
    }
    else 
        callback(null, {
            perimeter: function(l,w) {
                return (2*(l+w));
            },
            area: function(l,w) {
                return (l*w);
            }
    });
 }
catch (error) {
    callback(error,null);
}
}

文件2：solve-3.js

var argv = require('yargs')
.usage('Usage: node $0 --l=[number] --w=[number]')
.demand(['l','w'])
.argv;


var rect = require('./rect-2');

function solveRect(l,w) {
    console.log("Solving for rectangle with length: " + l + " and      width: " + w);

rect(l,w, function(err,rectangle) {
    if (err) {
        console.log(err);
    }
    else {
        console.log("The area of a rectangle with length = "+l+" and width = "+w+" is "+rectangle.area());
        console.log("The perimeter of a rectangle with length = "+l+" and width = "+w+" is "+rectangle.perimeter());
    }
  });
};

solveRect(Number(argv.l),Number(argv.w));

Answer 1

查看您定义的功能：

a = {'A': {'B': 1, 'C': 3}}

您希望此函数采用两个参数。

然后你没有参数调用它：

#include <stdio.h>
#include <stdlib.h>
#include <math.h>

int main(void)
{
int x, y;
float a,t;
//Inputs
printf("What is the speed that the jet is traveling in km/hr? \nWhat is the distance traveled in meters? \n");
scanf("%d , %d", &x, &y );


//Calculations

a = x * 1 / 60 * 1 / 60 * 1 / 60 * 1000 ;

t = sqrt( y * a / 2  ) ;

//Outputs
printf("The acceleration of the jet is %f meters per second squared. \n", a);
printf("The time it takes for the jet to reach takeoff speed is %f seconds. \n", t);

return 0;
}

您定义的参数是在rect-2文件的较高范围内隐藏的参数。一个简单的解决方法就是删除函数参数：

perimeter: function(l,w) {
    return (2*(l+w));
},

现在，这两个函数被称为“关闭”较高范围内的rectangle.perimeter()和perimeter: function() { return (2*(l+w)); }, area: function() { return (l*w); }变量。

虽然在l中包装字符串在这种情况下在技术上会起作用，但请注意w允许您在命令行上指定用户输入值的类型，例如.number()语法：

Number()

node.js（yargs）数字是作为字符串输入的？

1 个答案: