ljharb/qs

Parse results in multiple objects with the same key instead of one.

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#241 opened on Dec 20, 2017

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 (0 comments) (3 reactions) (0 assignees)JavaScript (8,015 stars) (744 forks)batch import
bughelp wanted

Description

The following stringify/parse sequence works as expected:

dataB = {
  "incidents": [
    {
      "open": [
        "damaged",
        {
          "lost": [
            "red",
            "green"
          ]
        }
      ]
    }
  ]
};

queryStringB = QS.stringify(dataB, { arrayFormat: 'brackets' });
parsedB = QS.parse(queryStringB)

The result is {"incidents":[{"open":["damaged",{"lost":["red","green"]}]}]}, which matches dataB.

However, the following sequence does not result how I expect it to:

dataA = {
  "incidents": [
    "cold",
    {
      "open": [
        "damaged",
        {
          "lost": [
            "red",
            "green"
          ]
        }
      ]
    }
  ]
};

queryStringA = QS.stringify(dataA, { arrayFormat: 'brackets' });
parsedA = QS.parse(queryStringA)

This results in {"incidents":["cold",{"open":["damaged"]},{"open":[{"lost":["red","green"]}]}]}, which does not match dataA. Note that the only difference between dataA and dataB is that dataA has an extra element in the incidents array.

I saw some other parsing issues in the issue listing but none of them look quite like this.

Contributor guide

Tech stack
javascript
Domain
backend
Issue type
bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
half day
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
stale
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
mostly clear
Prerequisites
JavaScriptquerystring parsing concepts
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
25
Research direction
Investigate the parsing logic in the qs library, specifically how it handles nested arrays with mixed primitive and object types. Reproduce the issue using the provided example and examine the parse function's handling of array brackets format. Look for code that merges keys incorrectly when arrays contain both strings and objects. The fix likely involves adjusting the logic that accumulates nested objects within arrays.