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JSON-vs-JavaScript-values.md

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JSON v.s. JavaScript values

The grammar structure of JSON is less complex than JavaScript object literals. Because JSON is designed for data exchange, serialization and deserialization would be frequently. A simple scheme and exclusion of language specific features is the way to go.

Types

Those types are allowed in JSON only:

  • String
  • Number
  • Object
  • Array
  • Boolean: true, false
  • null

Thus, literals like undefined and Infinity are all invalid.

Comments

Comments are not supported. Neither // nor /* */.

Keys

The keys are strings. The rules apply to String also apply to the keys.

Comma

Dangling tail comma is not allowed, thus:

{
  a: 1,
  b: 1,
}

The final comma is invalid.

Strings

Strings must be wrapped by doubled quotes "; Strings starting with single quotes ' and grave accent ```(string interpolation) are invalid.

Numbers

  • Format

    JSON values human-readability. So it is agnostic about number formats.

    • Extra positive sign in JSON is not invalid, e.g. +1.
    • Redudant 0s in head is considered invalid, thus 001, 00.1 are all invalid in JSON;
    • Numbers must be decimal system; not hexadecimal or others, thus, 0x01 is in valid in JSON;

  • Precision

    JSON spec has no limit in number precisions, while JavaScript does.

    Conversion from JSON to JavaScript may cause precision loss in number.