JavaScript Need help with JavaScripts reduce() function

[learningToCode321456]

Hey!

I'm learning JS by myself, and I've found a piece of code i'm not able to understand [may seem easy for you, but i'm a beginner 🙂]

Why does the following code display '0' in the console?

const sum = (...args) => {
    return args.reduce((a, b) => a + b, 0);
}

console.log(sum());

Thx for your help!!

 

[menator01]

I'm not really familiar with javascript but,
You did not enter any values in the function call
0 may be the default value set to return

const sum = (...args) => {
    return args.reduce((a, b) => a + b, 0);
}

console.log(sum(5,5));

#output
10

 

[CodeFilez]

@menator01 is exactly correct. There were no arguments passed and the starting value is zero.
The args variable is passed and set as an array by the spread operator.
reduce can take the two parameters a being the element of the array as it loops through it and b being the value stored in memory, which is defined with a starting value of zero.
so imagine reduce loops through the elements represented by a and adds b to it, which is stored in memory
[1,2,3] would be processed as the following:

1 + 0 = 1
2 + 1 = 3
3 + 3 = 6
That's a messy explanation but I hope that made sense.