箭头功能的意外输出

Question

我有以下箭头功能。

var a = 10;
var b = 5;
var str = (a,b) => ("sum: "+(a+b));

str();

我预计输出为

sum: 15

但输出是

sum: NaN

为什么？

Answer 1

var a = 10;

var b = 5;

var str = (a, b) => ("sum: " + (a + b));

str(a, b); // You have to call the function with parameters. 

Answer 2

您必须传递参数str(a,b)。

var a = 10;
var b = 5;
var str = (a,b) => ("sum: "+(a+b));

str(a,b);

Answer 3

您没有在调用函数

中传递参数a和b

＆＃13;

＆＃13;

var a = 10;
var b = 5;
var str = (a, b) => ("sum: " + (a + b));
console.log(str(a, b));

＆＃13;

＆＃13;

＆＃13;