Is the Order of a JSON Array Dependable?

When working with JSON, it's clear that relying on the ordering of key-value pairs may not be reliable. For instance, a JSON parser could interpret

{
    "someKey" : "someValue",
    "anotherKey" : "anotherValue",
    "evenAnotherKey" : "evenAnotherValue"
}

differently as

{
    "anotherKey" : "anotherValue",
    "someKey" : "someValue",
    "evenAnotherKey" : "evenAnotherValue"
}

which is legal. But what about the ordering in a JSON array? Could a JSON parser interpret

{
    "arrayKey" : ["firstElement", "secondElement", "thirdElement"]
}

as

{
    "arrayKey" : ["secondElement", "firstElement1", "thirdElement"]
}

legally? My assumption was no, but my friend argued otherwise.

javascriptjson

Answer №1

Absolutely! Arrays are specifically designed with the concept that order is important, setting them apart from Objects. This distinction is particularly notable in JavaScript and JSON.

Answer №2

Sequential data structures such as arrays and lists are always arranged in a specific order, with each element being assigned an index to indicate its position.

Interestingly, starting from ES5 version of JavaScript, the order of key-value pairs within objects is also ensured. However, this ordering system is not as straightforward as that of arrays and lists.

In objects, keys that are numeric are prioritized over non-numeric keys, and they are sorted in ascending numerical order. On the other hand, all other keys maintain their insertion order. For instance, consider the following object:

{
  hello : "world",
  foo : "bar",
  "22" : "first"
}

It will be displayed as:

{
  "22" : "first",
  hello : "world",
  foo : "bar"
}

Presently, major browsers and node.js adhere to this sorting rule, although some JavaScript transpilers (such as Babel) may not fully support it.

Personally, I prefer not to view unordered data structures like objects as ordered. However, the JavaScript community seems to have a different stance on this matter. For example, Go intentionally shuffles the mapping order to prevent users from relying on any accidental predictability in the language's implementation.

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