Optional initialValue?
Sometimes, we can see code using reduce without initialValue. For example,
const array = [1, 2, 3];
array.reduce((re, v) => re + v);According to mdn, it is valid and seems simpler. However, is it a good practice?
Cons Brought by No initialValue
In the real world, array could be []. In this case,
const array = [];
array.reduce((re, v) => re + v);You will got error in production!
Uncaught TypeError: Reduce of empty array with no initial value
Also, imagine that if you have met this code in your work ? What the hell does this reduce do?
- Join the
string - Or cumulative summation
- Or other situations?
You would never know until you have read the context.
As you can see, these are the most obvious cons brought by no initialValue.
- Potential Error
- Unclear semantics
Benefits Brought with initialValue
Instead, if using reduce with initialValue. For example, in the above case, we can write like this
const array = [];
array.reduce((re, v) => re + v, 0);- We would never meet the error!
- It is obvious that
reduceis using to do the cumulative summation job.
Safer and Clearer!
Issue
Source