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Some Things About JSON That You May Have Missed

John Au-Yeung on January 04, 2020

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Pacharapol Withayasakpunt • Jan 4 '20 • Edited

Another hidden ability of JavaScript JSON is Date.prototype.toJSON, which will customize JSON.stringify behavior of the object.

John Au-Yeung • Jan 4 '20

Thanks for finding that.

That's a method that most people don't think of using.

Stephen Irving • Jan 6 '20 • Edited

Just so you know, including multiple return paths for functions is an anti-pattern/code-smell. It is a best practice for a function to only have a single return path if that is possible. So, for example, in your third to last snippet, you could have written the replacer function like this instead and have what it returns be the same (I also fixed your NaN check to use Number.isNaN() because using equality to check against NaN will not work as expected):

const replacer = (key, value) => (
  typeof value === 'undefined'
    ? 'undefined'
    : (
      value instanceof Function || Number.isNaN(value) || value === Infinity
        ? value.toString()
        : value
    )
);

PeterGabriel2 • Jan 9 '20 • Edited

Absolutely wrong! In every case is switch more readable than joined or/and superlongline. More easy to update. And you will not make error in it so easily like in bunch of writeonly code you just wrote.

John Au-Yeung • Jan 10 '20

I think ternary operator shouldn't be nested. It's harder to read than if or switch like you said.

Nico Jansen • Jan 5 '20

value === NaN is always false. For example NaN === NaN. Use isNaN().

John Au-Yeung • Jan 6 '20

Thanks. That's a good catch.

Stephen Irving • Jan 6 '20

You should actually be using Number.isNan() over the global isNaN function which will give somewhat unexpected results in comparison to the newer method on the Number object. You should also use !Number.isFinite() instead of checking equality with Infinity.