What is the reason for JSON.parse throwing errors on the same strings that eval does not?

Question

What is the reason for JSON.parse throwing errors on the same strings that eval does not?

Imagine having something like this:

var a = '["\t"]'

When you use:

eval('var result = ' + a)

Everything runs smoothly. However, if you try:

var result = JSON.parse(a)

You'll encounter an error: Unexpected token.
The same issue arises with \b and \f: they work with eval but fail with JSON.parse. Why is that? Shouldn't the parser handle "\t" in a consistent manner?

Additionally, both eval and JSON.parse will fail with \n (as expected), but they also both fail with \r. Why does this happen?

There seems to be some confusion here, so could someone explain what's happening? It would be helpful to understand how the parser behaves in these two scenarios.

javascript json eval

Answer 1

Answer №1

In order to properly encode the backslash in a JavaScript string, you need to use double backslashes like this:

var b = '["\\t"]'

If you require more information on this topic, I recommend visiting "http://json.org/"

Answer 2

In order to properly encode the backslash in a JavaScript string, you need to use double backslashes like this:

var b = '["\\t"]'

If you require more information on this topic, I recommend visiting "http://json.org/"

Answer 3

Answer №2

The reason for this error is that the JSON format is not valid.

It's best to avoid manually writing JSON. Instead, utilize the JSON.stringify method to correctly encode your data.

var json = JSON.stringify(["\t"]);
JSON.parse(json);
//=> ["\t"]

Answer 4

The reason for this error is that the JSON format is not valid.

It's best to avoid manually writing JSON. Instead, utilize the JSON.stringify method to correctly encode your data.

var json = JSON.stringify(["\t"]);
JSON.parse(json);
//=> ["\t"]

What is the reason for JSON.parse throwing errors on the same strings that eval does not?

Answer №1

Answer №2

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