如何在JavaScript中实现保护子句? [英] How do you implement a guard clause in JavaScript?

问题描述

我想保护我的函数免受空值影响，并且仅在存在已定义"值的情况下继续操作.

I want to guard my functions against null-ish values and only continue if there is "defined" value.

查看之后

After looking around the solutions suggested to double equal to undefined: if (something == undefined). The problem with this solution is that you can declare an undefined variable.

所以我当前的解决方案是检查null if(something == null)，这会隐式检查undefined.如果我想捕获其他虚假值，请检查 if(something).

So my current solution is to check for null if(something == null) which implicetly checks for undefined. And if I want to catch addionalty falsy values I check if(something).

在此处查看测试: http://jsfiddle.net/AV47T/2/

现在我在这里想念什么吗?

Now am I missing something here?

Matthias

推荐答案

标准的JS保护措施是:

The standard JS guard is:

if (!x) {
    // throw error
}

！x 将捕获任何 undefined ， null ， false ， 0 ，或空字符串.

!x will catch any undefined, null, false, 0, or empty string.

如果要检查值是否为有效，则可以执行以下操作:

If you want to check if a value is valid, then you can do this:

if (Boolean(x)) {
    // great success
}

在本段中，如果x为但 undefined ， null ， false ， 0 或空字符串.

In this piece, the block is executed if x is anything but undefined, null, false, 0, or empty string.

-tjw

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