作为函数参数传递的字符串未定义 [英] String passed as function parameter is undefined

问题描述

当我将字符串作为参数传递给函数时，它返回 undefined .为什么会这样?

When I pass a string to a function as a parameter, it returns undefined. Why is that?

let a = 'b';

let test = (a) => console.log(a);

test(); // undefined

推荐答案

调用 test(); 时，您不会在(和)，因此您不会传递任何参数.

When you call test(); you aren't putting anything between ( and ), so you aren't passing any parameters.

在定义 test (使用(a)=> )时，您创建了 local 变量 a 会屏蔽具有相同名称的 global 变量.

When you defined test (with (a) =>) you created a local variable a that masks the global variable with the same name.

要通过 a ，您必须实际通过它: test(a).

To pass a you have to actually pass it: test(a).

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