Error "Uncaught SyntaxError: Unexpected token with JSON.parse"

Question

What causes this error on the third line?

var products = [{
  "name": "Pizza",
  "price": "10",
  "quantity": "7"
}, {
  "name": "Cerveja",
  "price": "12",
  "quantity": "5"
}, {
  "name": "Hamburguer",
  "price": "10",
  "quantity": "2"
}, {
  "name": "Fraldas",
  "price": "6",
  "quantity": "2"
}];
console.log(products);
var b = JSON.parse(products); //unexpected token o

^{Open console to view error}

Answer 1

products is an object. (creating from an object literal)

JSON.parse() is used to convert a string containing JSON notation into a Javascript object.

Your code turns the object into a string (by calling .toString()) in order to try to parse it as JSON text.
The default .toString() returns "[object Object]", which is not valid JSON; hence the error.

Answer 2

Let's say you know it's valid JSON, but you’re are still getting this...

In that case, it's likely that there are hidden/special characters in the string from whatever source your getting them. When you paste into a validator, they are lost - but in the string they are still there. Those characters, while invisible, will break JSON.parse().

If s is your raw JSON, then clean it up with:

// Preserve newlines, etc. - use valid JSON
s = s.replace(/\\n/g, "\\n")
               .replace(/\\'/g, "\\'")
               .replace(/\\"/g, '\\"')
               .replace(/\\&/g, "\\&")
               .replace(/\\r/g, "\\r")
               .replace(/\\t/g, "\\t")
               .replace(/\\b/g, "\\b")
               .replace(/\\f/g, "\\f");
// Remove non-printable and other non-valid JSON characters
s = s.replace(/[\u0000-\u0019]+/g,"");
var o = JSON.parse(s);

Answer 3

It seems you want to stringify the object, not parse. So do this:

JSON.stringify(products);

The reason for the error is that JSON.parse() expects a String value and products is an Array.

Note: I think it attempts json.parse('[object Array]') which complains it didn't expect token o after [.

Answer 4

JSON.parse is waiting for a String in parameter. You need to stringify your JSON object to solve the problem.

products = [{"name":"Pizza","price":"10","quantity":"7"}, {"name":"Cerveja","price":"12","quantity":"5"}, {"name":"Hamburguer","price":"10","quantity":"2"}, {"name":"Fraldas","price":"6","quantity":"2"}];
console.log(products);
var b = JSON.parse(JSON.stringify(products));  //solves the problem

Answer 5

I found the same issue with JSON.parse(inputString).

In my case, the input string is coming from my server page (return of a page method).

I printed the typeof(inputString) - it was string, but still the error occurs.

I also tried JSON.stringify(inputString), but it did not help.

Later I found this to be an issue with the new line operator [\n], inside a field value.

I did a replace (with some other character, put the new line back after parse) and everything was working fine.

Answer 6

You should validate your JSON string here.

A valid JSON string must have double quotes around the keys:

JSON.parse({"u1":1000,"u2":1100})       // will be ok

If there are no quotes, it will cause an error:

JSON.parse({u1:1000,u2:1100})    
// error Uncaught SyntaxError: Unexpected token u in JSON at position 2

Using single quotes will also cause an error:

JSON.parse({'u1':1000,'u2':1100})    
// error Uncaught SyntaxError: Unexpected token ' in JSON at position 1

Answer 7

products = [{"name":"Pizza","price":"10","quantity":"7"}, {"name":"Cerveja","price":"12","quantity":"5"}, {"name":"Hamburguer","price":"10","quantity":"2"}, {"name":"Fraldas","price":"6","quantity":"2"}];

change to

products = '[{"name":"Pizza","price":"10","quantity":"7"}, {"name":"Cerveja","price":"12","quantity":"5"}, {"name":"Hamburguer","price":"10","quantity":"2"}, {"name":"Fraldas","price":"6","quantity":"2"}]';

Answer 8

If there are leading or trailing spaces, it'll be invalid. Trailing and leading spaces can be removed as

mystring = mystring.replace(/^\s+|\s+$/g, "");

Source: JavaScript: trim leading or trailing spaces from a string

Answer 9

Here's a function I made based on previous replies: it works on my machine but YMMV.

/**
   * @description Converts a string response to an array of objects.
   * @param {string} string - The string you want to convert.
   * @returns {array} - an array of objects.
  */
function stringToJson(input) {
  var result = [];

  // Replace leading and trailing [], if present
  input = input.replace(/^\[/, '');
  input = input.replace(/\]$/, '');

  // Change the delimiter to
  input = input.replace(/},{/g, '};;;{');

  // Preserve newlines, etc. - use valid JSON
  //https://stackoverflow.com/questions/14432165/uncaught-syntaxerror-unexpected-token-with-json-parse
  input = input.replace(/\\n/g, "\\n")
               .replace(/\\'/g, "\\'")
               .replace(/\\"/g, '\\"')
               .replace(/\\&/g, "\\&")
               .replace(/\\r/g, "\\r")
               .replace(/\\t/g, "\\t")
               .replace(/\\b/g, "\\b")
               .replace(/\\f/g, "\\f");

  // Remove non-printable and other non-valid JSON characters
  input = input.replace(/[\u0000-\u0019]+/g, "");

  input = input.split(';;;');

  input.forEach(function(element) {
    //console.log(JSON.stringify(element));

    result.push(JSON.parse(element));
  }, this);

  return result;
}

Answer 10

One other gotcha that can result in "SyntaxError: Unexpected token" exception when calling JSON.parse() is using any of the following in the string values:

1. New-line characters.

2. Tabs (yes, tabs that you can produce with the Tab key!)

3. Any stand-alone slash \ (but for some reason not /, at least not on Chrome.)

(For a full list see the String section here.)

For instance the following will get you this exception:

{
    "msg" : {
        "message": "It cannot
contain a new-line",
        "description": "Some discription with a     tabbed space is also bad",
        "value": "It cannot have 3\4 un-escaped"
    }
}

So it should be changed to:

{
    "msg" : {
        "message": "It cannot\ncontain a new-line",
        "description": "Some discription with a\t\ttabbed space",
        "value": "It cannot have 3\\4 un-escaped"
    }
}

Which, I should say, makes it quite unreadable in JSON-only format with larger amount of text.

Answer 11

My issue was that I had commented HTML in a PHP callback function via Ajax that was parsing the comments and return invalid JSON.

Once I removed the commented HTML, all was good and the JSON was parsed without any issues.

Answer 12

When you are using the POST or PUT method, make sure to stringify the body part.

I have documented an example here at https://gist.github.com/manju16832003/4a92a2be693a8fda7ca84b58b8fa7154

Answer 13

[
  {
    "name": "Pizza",
    "price": "10",
    "quantity": "7"
  },
  {
    "name": "Cerveja",
    "price": "12",
    "quantity": "5"
  },
  {
    "name": "Hamburguer",
    "price": "10",
    "quantity": "2"
  },
  {
    "name": "Fraldas",
    "price": "6",
    "quantity": "2"
  }
]

---

Here is your perfect JSON content that you can parse.

Answer 14

The only mistake is you are parsing an already-parsed object, so it's throwing an error. Use this and you will be good to go.

var products = [{
  "name": "Pizza",
  "price": "10",
  "quantity": "7"
}, {
  "name": "Cerveja",
  "price": "12",
  "quantity": "5"
}, {
  "name": "Hamburguer",
  "price": "10",
  "quantity": "2"
}, {
  "name": "Fraldas",
  "price": "6",
  "quantity": "2"
}];
console.log(products[0].name); // Name of item at 0th index

If you want to print the entire JSON content, use JSON.stringify().

Answer 15

products is an array which can be used directly:

var i, j;

for(i=0; i<products.length; i++)
  for(j in products[i])
    console.log("property name: " + j, "value: " + products[i][j]);

Answer 16

Now apparently \r, \b, \t, \f, etc. aren't the only problematic characters that can give you this error.

Note that some browsers may have additional requirements for the input of JSON.parse.

Run this test code in your browser:

var arr = [];
for(var x=0; x < 0xffff; ++x){
    try{
        JSON.parse(String.fromCharCode(0x22, x, 0x22));
    }catch(e){
        arr.push(x);
    }
}
console.log(arr);

Testing on Chrome, I see that it doesn't allow JSON.parse(String.fromCharCode(0x22, x, 0x22)); where x is 34, 92, or from 0 to 31.

Characters 34 and 92 are the " and \ characters respectively, and they are usually expected and properly escaped. It's characterss 0 to 31 that would give you problems.

To help with debugging, before you do JSON.parse(input), first verify that the input doesn't contain problematic characters:

function VerifyInput(input){
    for(var x=0; x<input.length; ++x){
        let c = input.charCodeAt(x);
        if(c >= 0 && c <= 31){
            throw 'problematic character found at position ' + x;
        }
    }
}

Answer 17

Oh man, solutions in all previous answers didn't work for me. I had a similar problem just now. I managed to solve it with wrapping with the quote. See the screenshot. Whoo.

Original:

var products = [{
  "name": "Pizza",
  "price": "10",
  "quantity": "7"
}, {
  "name": "Cerveja",
  "price": "12",
  "quantity": "5"
}, {
  "name": "Hamburguer",
  "price": "10",
  "quantity": "2"
}, {
  "name": "Fraldas",
  "price": "6",
  "quantity": "2"
}];
console.log(products);
var b = JSON.parse(products); //unexpected token o

Answer 18

The error you are getting, i.e., "unexpected token o", is because JSON is expected, but an object is obtained while parsing. That "o" is the first letter of word "object".

Answer 19

It can happen for a lot of reasons, but probably for an invalid character, so you can use JSON.stringify(obj); that will turn your object into a JSON, but remember that it is a jQuery expression.

Answer 20

In my case there are the following character problems in my JSON string:

1. \r
2. \t
3. \r\n
4. \n
5. :
6. "

I have replaced them with other characters or symbols, and then reverted back again from coding.

Answer 21

This is now a JavaScript array of objects, not JSON format. To convert it into JSON format, you need to use a function called JSON.stringify().

JSON.stringify(products)

Answer 22

Why do you need JSON.parse? It's already in an array-of-object format.

Better use JSON.stringify as below:

var b = JSON.stringify(products);

Answer 23

The mistake I was doing was passing null (unknowingly) into JSON.parse().

So it threw Unexpected token n in JSON at position 0.

But this happens whenever you pass something which is not a JavaScript Object in JSON.parse().

Answer 24

Use eval. It takes JavaScript expression/code as string and evaluates/executes it.

eval(inputString);