"Uncaught (in promise): SyntaxError: Unexpected token ' in JSON at position 2" How to fix this error?

Question

getting the same error in JSON, user is the textbox value which is then pass in JSON for setting class level permissions in parse server

var cc = "role:" + user;
var jsonParam = "{ 'classLevelPermissions' :
                    { 'get':
                        { '*': true, '" + cc + "'  :  true },
                      'find':
                        {'*': true,'" + cc + "'  :  true },
                      'create':
                        { '" + cc + "'  :  true },
                      'update':
                        { '" + cc + "' :  true },
                      'delete':
                        { '" + cc + "'  :  true }
                    }
                 }";
const result = this.http.post(this.url,
    {
        "reqparam": JSON.parse(jsonParam)
    }, httpOptions).toPromise();
console.log(result);

please help me to solve this.

score 1 · Answer 1 · answered Nov 14 '19 at 09:10

Welcome to StackOverflow :)!

You get a syntax error while parsing JSON because the JSON you wrote contains a single quote ', which is an invalid character in JSON. Instead of single quotes ' you should use double quotes ".

To include double quotes in a JavaScript string you will have to escape them. There is another StackOverflow answer pointing that out: https://stackoverflow.com/a/21672439/7437032

Applied to your use case that means changing the jsonParam like this:

var jsonParam = "{ \"classLevelPermissions\" : { \"get\": { \"*\": true, \"" + cc + "\"  :  true }, \"find\": {\"*\": true,\"" + cc + "\"  :  true }, \"create\": { \"" + cc + "\"  :  true }, \"update\": { \"" + cc + "\" :  true }, \"delete\": { \"" + cc + "\"  :  true } } }";

Since this is not very readable and you have multiple variables in your string I propose using JavaScript template strings instead. (Just for clean code ) Here is the documentation for JavaScript template strings: https://developer.mozilla.org/de/docs/Web/JavaScript/Reference/template_strings

Applied to your use case:

var jsonParam = `{ "classLevelPermissions" : { "get": { "*": true, "${cc}"  :  true }, "find": {"*": true,"${cc}"  :  true }, "create": { "${cc}"  :  true }, "update": { "${cc}" :  true }, "delete": { "${cc}"  :  true } } }`;

score 0 · Answer 2 · answered Nov 14 '19 at 09:09

Wrap the text in `` (backticks) and use double quotes for json keys, pass cc as string interpolation.This should fix parse error.

var cc = "role:" + user;
var jsonParam = `{ "classLevelPermissions" : { "get": { "*": true, " ${cc} "  :  true }, "find": {"*": true," ${cc}"  :  true }, "create": { " ${cc}"  :  true }, "update": { "${cc}" :  true }, "delete": { " ${cc} "  :  true } } }`;

"Uncaught (in promise): SyntaxError: Unexpected token ' in JSON at position 2" How to fix this error?

2 Answers2