轻松执行Node.js程序可打印不确定的结果

Question

I'm working on the Baby Steps part of "learnyounode", the interactive Node.js tutorial.

Write a program that accepts one or more numbers as command-line arguments and prints the sum of those numbers to the console (stdout).

Since I know JavaScript from before, I thought it would be rather simple:

var sum = 0;
for (var i = 2; i < process.argv.length; i++) {
  console.log('Adding ' + process.argv[i]);
  sum += Number(process.argv[i]);
}

console.log(sum)

I can't see any problem with this piece of code, but the results seem indeterministic to me!

d:\repos\github\damd\learnyounode>learnyounode run baby_steps.js 1 2 3
Adding 1
Adding 72
Adding 45
Adding 32
150

d:\repos\github\damd\learnyounode>learnyounode run baby_steps.js
Adding 22
Adding 41
Adding 85
Adding 38
186

d:\repos\github\damd\learnyounode>learnyounode run baby_steps.js 10 20 30
Adding 60
Adding 25
Adding 96
Adding 24
Adding 76
Adding 96
Adding 21
Adding 53
Adding 6
Adding 51
Adding 87
Adding 29
Adding 2
Adding 21
Adding 28
Adding 47
Adding 18
Adding 89
829

What's going on here? I'm using Node.js v0.10.34 on Windows 7.

Answer 1

The learnyounode in the run functionality supplies arguments of its own (that you are not aware of) without being asked to and ignores your own arguments.

You should run your file calling the good ol' node executable like this:

node baby_steps.js

Instead of calling the learnyounode executable:

learnyounode run baby_steps.js

Answer 2

Note that the verify program expected non deterministic values... Maybe this exercise just intended to use the input as the vector index number (direction) regardless itself value.

The reason why those numbers can seems non deterministic could be that argvs[] vector is used to carry non-static values of enviroment (also you're running node on index zero).

Remember, learnyounode run function provides you a test enviroment by randomizing the inputs.

Anyway there's a great walkthrough on Github:

https://github.com/leochilds/learnyounode-walkthrough