The basic idea of the lodash reject method is to pass an array, or collection object of any kind as the first argument. Then for the second argument pass a method that will be used to return a boolean value that will be used to reject any values that will result in a true value.
the lodash reject method is just an inversion of the lodash filter method. So with that said the reject method in lodash is a little redundant as it would not be to hard to just negate the result of the expression that is returned with the method that is used to filter elements.
So there is the native array filter prototype method that could quickly be used to create a reject method that would work the same way when it comes to arrays, and not using any kind of short hand value what is used to reject array elements.
I would say that the lodash reject method is yet another methods in lodash that does not help with the argument as to why it is that developers should bother with lodash when writing new code. Do not get my wrong there are of course reasons why using lodash, or better yet my own custom utility library. It is just that I can not say that the lodash reject methods is the most compelling reason why one should bother. It seems to me that there are only a few select methods that I would actually use, and in real projects I will find myself just installing that small collection of methods. When it comes to rejecting, or filtering in mist cases I would just use the native methods for that these days.