JSON.parse输出一个字符串

Question

What's going on here?

var data = '"[2743,1,1,1,1,1]"';
var flags = JSON.parse(data);
console.log(typeof flags);      // this outputs "string"

I was expecting flags to be an object or array, but it's a string. The MDN Web Docs say, "The JSON.parse() method parses a JSON string, constructing the JavaScript value or object described by the string." Also:

Return value
The Object corresponding to the given JSON text.

Exceptions
Throws a SyntaxError exception if the string to parse is not valid JSON.

Answer 1

var data = '"[2743,1,1,1,1,1]"';

This is a string containing a string. When you parse it with

var result = JSON.parse(data);

What you get is the string

"[2743,1,1,1,1,1]"

If you parse that a second time you will get your array of flags.

Try this

var flags = JSON.parse(JSON.parse(data));

Answer 2

Looks like it's an object and everything's OK, check the snippet:

 var data = '[2743,1,1,1,1,1]'; var flags = JSON.parse(data); console.log(typeof flags); console.log(flags);