在JavaScript中使用身份函数 [英] Use of the identity function in JavaScript

问题描述

 函数标识（值）{
返回值; 
 
 
 
 $ b $ p 
 $ b原因是我经常需要区分原始类型（ undefined ， null ，布尔值， code>和 string ）和对象类型（ object 和 function >）由 typeof 运算符返回。我觉得使用这个用例的indentity函数非常简单： 
 
 
  if（new identity（value）== value）; // value是一个对象类型
 if（new identity（value）！= value）; //值是原始类型
  
身份函数比下面的代码小得多：  
 
 
 函数isObject（value）{
 var type = typeof value; 
返回类型==对象||键入==函数;然而，在阅读我的代码时，我的一位朋友抱怨说我的黑客有误导性，比上述替代方案计算量更大。
 
 
 
我不想从我的任何程序中删除此功能，因为我相信这是一个优雅的破解。然后，我再也不为自己编写程序。有没有其他的用例在JavaScript中的身份识别功能？
解决方案
我更新了我的 speedtest 来测试是否返回正确的结果......它们不是：
 
 
 
如果与新身份（x）== x 进行比较，则 null 被视为一个对象。  === 可以工作。
 
 
 
这样的陷阱有利于 isObject ...）解决方案。
 
 
 
如果您比较 ==='object' / 'function'在 isObject 代码中，那么它的速度将比原始实现快两倍，第三次比新身份（x）=== x 。
 
快
I use the identity function in all my JavaScript programs:
function identity(value) {
    return value;
}
The reason is that I often need differentiate between primitives types (undefined, null, boolean, number and string) and object types (object and function) as returned by the typeof operator. I feel using the indentity function for this use case very succuint:
if (new identity(value) == value); // value is of an object type
if (new identity(value) != value); // value is of a primitive type
The identity function is much smaller and simpler than the following code:
function isObject(value) {
    var type = typeof value;
    return type == "object" || type == "function";
}
However on reading my code a friend of mine complained that my hack is misleading and more computationally expensive than the above alternative.

I don't want to remove this function from any of my programs as I believe it's an elegant hack. Then again I don't write programs solely for myself. Is there any other use case for the identity function in JavaScript?
解决方案
I updated my "speedtest" to test if the right results are returned … they aren't:

If you compare with new identity(x) == x, then null is deemed an object. === works, though.

Such pitfalls speak in favor of the isObject(...) solution.

If you compare === 'object'/'function' in the isObject code, then it will be double as fast as your original implementation, and almost a third faster than new identity(x) === x.

                        
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