I have try the additional argumets of JSON.stringify in FireFox, and I got this result:

JSON.stringify({a:[{b:1},{b:2}],c:{d:{e:false}},f:[1,2,'123']}, null, '\t');
// get the string format below:
{
	"a": [
		{
			"b": 1
		},
		{
			"b": 2
		}
	],
	"c": {
		"d": {
			"e": false
		}
	},
	"f": [
		1,
		2,
		"123"
	]
}

But what I want to realize is actually the format like below(Described in kata detail), which is the coding standars in my working Group:

{
    "a": [{
        "b": 1
    }, {
        "b": 2
    }],
    "c": {
        "d": {
            "e": false
        }
    },
    "f": [1, 2, "123"]
}

Between the "key" and the { , it should be a space instead of a '\t'

Sorry, that's my fault to give too few descriptions or examples of this Kata... And thank you for raising the question

It is awkward that I dont know the additional arguments of JSON.stringify API. One of my friends asked me how to get string with indentation from an object. Instead of searching the solution, I write a function for him... And then, I published this Kata which is the first Kata I have published. Thank you for remainding me. Maybe I should unpublished this Kata?

"shouldn't handle any nested functions:
Test Failed: Expected: 3, instead got: undefined"

I got an error like this when I sumbmitted.What does this mean?