What's the difference in using toString() compared to JSON.stringify()?

Question

In both the cases I get in output the content of the object:

alert(JSON.stringify(obj));

or

alert(obj.toString());
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Answer 1

Unless you have a custom object with custom .toString method returning JSON.stringify of that object, there is no obj that would give obj.toString() == JSON.stringify(obj).

When obj is an array like [1,2,3] then .toString() gives:

"1,2,3"

And JSON.stringify:

"[1,2,3]"

These are close but not quite the same, the JSON serialized one has no ambiguity with commas and directly runs as Javascript or can be parsed as JSON.

See:

["1,",2,3].toString();
//"1,,2,3" ... so you can't just split by comma and get original array
//it is in fact impossible to restore the original array from this result

JSON.stringify(["1,",2,3])
//'["1,",2,3]'
//original array can be restored exactly