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How works JSON.parse()

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JSON

JSON is defined recursively (recursive function calls itself until it finds something that stops). All Boolean, String, Number, Array (with valid JSONs), objects whose keys are strings and whose values ​​are valid JSONs and Null are valid JSONs.

.parse()

Initially, it is important to understand what the parse of the function would be. In JavaScript, it interprets a String, causing its contents to be read correctly by the computer. For this reason, the syntax for transforming the String "2" into Number, is parseInt().

O que é JSON.parse()

The JSON.parse() method is used when you want to parse a JSON String, and interpret it as a value/object in JavaScript. This implies a doubt about the functioning of other functions in JavaScript, such as Boolean(). JSON.parse() gets the string representation of a valid JSON.

Example:

console.log(typeof JSON.parse('true')) // boolean
console.log(typeof JSON.parse('false')) // boolean
console.log(typeof JSON.parse('20')) // number
console.log(Boolean('false')) // true

As said, JSON.parse() can transform the String JSON into a value/object in JavaScript, which is completely different from conversions like Boolean().

If JSON.parse("false") is false, why Boolean("false") is true?

Exactly because Boolean() is not treating a JSON String for value/object in JavaScript, but validating between false or true JavaScript conditions. This means that for something to be false, it needs to be: 0, -0, false, NaN, undefined or null, everything else like values, objects, array empty and a non-empty String is true, regardless of what content is in it.

Understanding these concepts helps in the use of JavaScript, with a better understanding of how the language works, consequently making you a better programmer, avoiding unnecessary discussions on social networks.

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