Create an object from pairs of key and value

Turn [key, value] pairs into a plain object with Object.fromEntries.

JavaScript Version 1.0.0 · MIT · .md

function toObject(pairs) { return Object.fromEntries(pairs); }

Input & expected output

[
  [
    "from",
    "[email protected]"
  ],
  [
    "to",
    "[email protected]"
  ],
  [
    "subject",
    "Order 8812 confirmed"
  ]
]

{
  "from": "[email protected]",
  "to": "[email protected]",
  "subject": "Order 8812 confirmed"
}

The edge case

[
  [
    "status",
    "deferred"
  ],
  [
    "status",
    "delivered"
  ]
]

{
  "status": "delivered"
}

Know the limits

• When a key repeats, the later pair wins, as the edge case shows.
• Keys become strings. A "__proto__" key becomes an ordinary own property, unlike assignment.

The function above is the implementation used by the lab. The lab validates JSON types and caps size before execution; include equivalent validation when accepting untrusted input in your application.

Keep exploring

• Pick properties from an object — Build a new object with only the requested own properties.
• Omit properties from an object — Keep the own enumerable fields that are not in a supplied list.
• Check if multiple objects are equal — Compare JSON serializations with the first object.