What happens here is that `JSON.stringify` cannot be used for circular data. Circular data is when you have an object that references some other parent object. If `JSON.stringify` printed some circular data, it would be a infinity string.
This probably happen because you are getting some circular data from the response.
If you really want to print it and ignore the circular that, you can take a look at [this question](https://stackoverflow.com/questions/11616630/how-can-i-print-a-circular-structure-in-a-json-like-format) that have alot of ways to do so.
What I recommend is using `console.log` instead of `alert` and in the console you will be able to see circular data with no problem.
Here is a demo for showing circular data, wich is taken from [this answer](https://stackoverflow.com/a/11616993/9119186).
<!-- begin snippet: js hide: false console: true babel: false -->
<!-- language: lang-js -->
// Demo: Circular reference
var o = {};
o.o = o;
// Note: cache should not be re-used by repeated calls to JSON.stringify.
var cache = [];
JSON.stringify(o, function(key, value) {
if (typeof value === 'object' && value !== null) {
if (cache.indexOf(value) !== -1) {
// Duplicate reference found, discard key
return;
}
// Store value in our collection
cache.push(value);
}
return value;
});
cache = null; // Enable garbage collection
var a = {b:1}
var o = {};
o.one = a;
o.two = a;
// one and two point to the same object, but two is discarded:
console.log(JSON.stringify(o))
<!-- end snippet -->
Use `JSON.stringify` with a custom replacer. For example:
// Demo: Circular reference
var o = {};
o.o = o;
// Note: cache should not be re-used by repeated calls to JSON.stringify.
var cache = [];
JSON.stringify(o, function(key, value) {
if (typeof value === 'object' && value !== null) {
if (cache.indexOf(value) !== -1) {
// Duplicate reference found, discard key
return;
}
// Store value in our collection
cache.push(value);
}
return value;
});
cache = null; // Enable garbage collection
The replacer in this example is not 100% correct (depending on your definition of "duplicate"). In the following case, a value is discarded:
var a = {b:1}
var o = {};
o.one = a;
o.two = a;
// one and two point to the same object, but two is discarded:
JSON.stringify(o, ...);
But the concept stands: Use a custom replacer, and keep track of the parsed object values.
