Question

105

Serialization of RegExp

rated 0 times [ 111] [ 6] / answers: 1 / hits: 20057 / 12 Years ago, wed, august 22, 2012, 12:00:00

So, I was interested to find that JSON.stringify reduces a RegExp to an empty object-literal (fiddle):

JSON.stringify(/^[0-9]+$/) // {}

Is this behavior expected? I realize that a RegExp is an object with no properties to serialize. That said, dates are objects too; yet JSON.stringify() manages to produce a meaningful string:

JSON.stringify(new Date) // 2014-07-03T13:42:47.905Z

I would have hoped that JSON would give RegExp the same consideration by using RegExp.prototype.toString().

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louiemarvinm

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3 Years ago

answered 12 Years ago tomas · Accepted Answer

Yes, because there's no canonical representation for a RegExp object in JSON. Thus, it's just an empty object.

edit — well it's 2018 now; the answers suggesting solutions using .toJSON() etc are probably fine, though I'd add the method to the prototype with

Object.defineProperty(RegExp.prototype, toJSON, {

  value: RegExp.prototype.toString

});

and so on. That ensures that the function name isn't enumerable, which makes the monkey-patch somewhat more hygienic.