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The JSON standard defines objects in one way and the ECMAScript (JavaScript) standard defines it in another.
It is often said that JSON objects are a subset of JavaScript objects, is this true?
Is every JSON object also a valid JavaScript object?
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An Object literal is when you declare an Object in JavaScript code which is a variable that stores data in key-value pairs, while JSON stands for JavaScript Object Notation and it's a language-agnostic format for storing and transferring data that is based on JavaScript Objects.
Any JSON text is a valid JavaScript expression, but only in JavaScript engines that have implemented the proposal to make all JSON text valid ECMA-262.
JSON objects are written in key/value pairs. JSON objects are surrounded by curly braces { } . Keys must be strings, and values must be a valid JSON data type (string, number, object, array, boolean or null). Keys and values are separated by a colon. Each key/value pair is separated by a comma.
The JSON format is syntactically identical to the code for creating JavaScript objects. Because of this similarity, a JavaScript program can easily convert JSON data into native JavaScript objects. The JSON syntax is derived from JavaScript object notation syntax, but the JSON format is text only.
Update 2019: the answer is now YES as of this proposal and JavaScript versions following ECMAScript 2019 (including) will be proper supersets.
The answer is "no". There are cases when JSON object won't be valid for JavaScript. JSON is NOT a JavaScript subset.
JSON
That is: due to JSON specification, you can safely use such characters, as U+2028 in any string. It is a unicode whitespace character. Not control or other special character.
JavaScript
Well, now in JavaScript. ECMA-262 has a little difference in its definition of strings. In section 7.8.4 there is a thing, that string can contain all things except quote, a backslash or a line terminator. Now what's line terminator? It's in section 7.3 :
As you can see, in JavaScript symbols U+2028 and U+2029 are not allowed.
This is a sample, but since we have at least one case of difference, it's well-enough to realize that answer is no
Image source & full description: timelessrepo
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