In JavaScript, num = num | | 1 What are the pros and cons of this notation?

Syntax sugar, equivalent to if (!! num = = false) Num=1; Java-like num=null? 1:num

The following is an answer from a friend who knows:

It's just a shorthand method. The advantage is shorter, but in fact the disadvantage is even greater.

Do you know exactly when it will become 1?

-When NUM has a value of 0 o'clock, it will become 1!
--When NUM has a value of Nan (which most likely means an error in the previous calculation), it becomes 1!
--In addition, when the incoming value type is wrong, your program may have an error, but after this statement, you may not get an error.

These are probably not the results you want, especially because many functions may add to the handling of the special value of 0 , which often leads to errors. Even if it happens to be the result you want, the next maintainer (including yourself after 1 months) may not be able to see it!

So personal advice in a certain size of the team or project, do not use | | Short-circuit, or honestly write:

if (num = = null) num = 1

The only exception is if you know exactly which is an object and cannot be a primitive value, it can be used.
option = Option | | Defaultoption

He Shijun
Source: https://www.zhihu.com/question/20377595/answer/14948746

In JavaScript, num = num | | 1 What are the pros and cons of this notation?