combinations suffers a performance issue under some arguments

[zyscoder]

Version

node v22.11.0
npm 10.9.0

Platform

Linux u24vm 6.8.0-48-generic #48-Ubuntu SMP PREEMPT_DYNAMIC Fri Sep 27 14:04:52 UTC 2024 x86_64 x86_64 x86_64 GNU/Linux

What steps will reproduce the bug?

2. Try to install the package: combinations

a. npm init -y
b. npm shrinkwrap
c. npm install --save combinations
d. npm audit fix

the final package.json is as follows:

{
  "name": "package-9256e4c379ff4a504a88c567d54dcb97",
  "version": "1.0.0",
  "main": "index.js",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1"
  },
  "keywords": [],
  "author": "",
  "license": "ISC",
  "description": "",
  "dependencies": {
    "combinations": "^1.0.0"
  }
}

2. Setup a node instance,

node

3. and run the following javascript code.

(async function() {
    var lib = await import('combinations');
    var result = lib.default(["a"], -2504920488, 2**64);;
    console.log(result);
})();

Then the node instance will hang and no response returned.

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

This issue can always be triggered following the steps above.

What is the expected behavior? Why is that the expected behavior?

No matter how to set the min and max parameters, the result will always be a subset of [ [ 'a' ] ]. It's not reasonable to stuck so much time here.

What do you see instead?

» node
Welcome to Node.js v22.11.0.
Type ".help" for more information.

(async function() {
... var lib = await import('combinations');
... var result = lib.default(["a"], -2504920488, 2**64);;
... console.log(result);
... })();
Promise {
,
[Symbol(async_id_symbol)]: 29,
[Symbol(trigger_async_id_symbol)]: 6
}
(the node server hanged here.)

[zyscoder]

suggested patch:

var combo = function(a, min, max) {
  min = min || 1;
  min = min > 1 ? min : 1;
  max = max < a.length ? max : a.length;
  var fn = function(n, src, got, all) {
    if (n == 0) {
      if (got.length > 0) {
        all[all.length] = got;
      }
      return;
    }
    for (var j = 0; j < src.length; j++) {
      fn(n - 1, src.slice(j + 1), got.concat([src[j]]), all);
    }
    return;
  }
  var all = [];
  for (var i = min; i < a.length; i++) {
    fn(i, a, [], all);
  }
  if(a.length == max) all.push(a);
  return all;
}
module.exports = combo;