Basic math not working right with numbers passed-in from process.argv[].

[robherc]

Version

17.8.1

Platform

Linux [my-computer-hostname] 5.13.0-35-generic #40~20.04.1-Ubuntu SMP Mon Mar 7 09:18:32 UTC 2022 x86_64 x86_64 x86_64 GNU/Linux

Subsystem

No response

What steps will reproduce the bug?

1: Assign numeric values from process.argv[] to variables declared with let (i.e. let x=process.argv[2]; let y=process.argv[3]; let z=process.argv[4]
2: Perform some basic arithmetic on those variables (i.e. let answer=x*(y+z);)
3: See ridiculous output (above answer would come out as x * y.concat(z);)

Testing code that I'm using:

let x   = process.argv[2];
let y   = process.argv[3];
let z   = process.argv[4];
console.log("Using values from process.argv[]:");
console.log(`x=${x} | y=${y} | z=${z}`);
console.log(`x-y=${x-y}\nx/y=${x/y}\nx*(y+z)=${x*(y+z)}`);

let a=1;
let b=2;
let c=3;
let answer=a*(b+c);
console.log("\n\nUsing values declared within the script:");
console.log(`a=${a} | b=${b} | z=${c}`);
console.log(`a-b=${a-b}\na/b=${a/b}\na*(b+c)=${a*(b+c)}`);

How often does it reproduce? Is there a required condition?

Always. Seems to be a variable type auto-detect error when using numeric values from process.argv[]

What is the expected behavior?

node mathbugtest.js 1 2 3 [Enter]
x=1 | y=2 | z=3
x-y=-1
x/y=0.5
x*(y+z)=5

What do you see instead?

node mathbugtest.js 1 2 3 [Enter]
x=1 | y=2 | z=3
x-y=-1
x/y=0.5
x*(y+z)=23

Additional information

No response

[cjihrig]

The values coming from process.argv are strings. The + operator performs string concatenation or addition, depending on the type of the values being used, while the -, *, and / operators convert the values to numbers first.

This is not specific to Node.js. You can try it in a browser or Deno as well. Closing as working as intended.