Uncaught SyntaxError Unexpected token u in JSON at position 0

Question

Only at the checkout and on individual product pages I am getting the following error in the console log   VM35594 1 Uncaught SyntaxError  Unexpected token u in JSON at position 0     at JSON parse   lt anonymous gt       at run  layout min js 9      at app min js 1     at main min js 2     at Object execCb  require min js 112      at Module check  require min js 56      at Module  lt anonymous gt   require min js 72      at require min js 11     at require min js 74     at each  require min js 3    I am using a one page checkout extension  but when I disable that the error still shows  I thought it might had something to do with the reviews on the product page  as I moved the reviews out of the tabs   but undoing that change didn t fix the error on the product pages

User · Answer

Your app is attempting to parse the undefined JSON web token. Such malfunction may occur due to the wrong usage of the local storage. Try to clear your local storage.

Example for Google Chrome:

F12
Application
Local Storage
Clear All

User · Answer

For me  that happened because I had an empty component in my page -    lt script type  text x-magento-init  gt            page messages             Magento Ui js core app                              Deleting this piece of code resolved the issue

User · Answer

As  Seth Holladay  MinusFour commented  you are parsing an undefined variable  Try adding an if condition before doing the parse     if  typeof test1      undefined       test2   JSON parse test1       Note  This is just a check for undefined case  Any other parsing issues still need to be handled

User · Answer

localStorage clear    That ll clear the stored data  Then refresh and things should start to work

User · Answer

Try this in the console   JSON parse undefined    Here is what you will get   Uncaught SyntaxError  Unexpected token u in JSON at position 0     at JSON parse   lt anonymous gt       at  lt anonymous gt  1 6   In other words  your app is attempting to parse undefined  which is not valid JSON   There are two common causes for this  The first is that you may be referencing a non-existent property  or even a non-existent variable if not in strict mode    window foobar      some   data     JSON parse window foobarn      oops  misspelled    The second common cause is failure to receive the JSON in the first place  which could be caused by client side scripts that ignore errors and send a request when they shouldn t   Make sure both your server-side and client-side scripts are running in strict mode and lint them using ESLint  This will give you pretty good confidence that there are no typos

User · Answer

I had this issue for 2 days  let me show you how I fixed it   This was how the code looked when I was getting the error   request onload   function            This is where we begin accessing the Json     let data   JSON parse this response       console log data      This is what I changed to get the result I wanted    request onload   function            This is where we begin accessing the Json     let data   JSON parse this responseText       console log data      So all I really did was change      this response to this responseText

User · Answer

This is due to the interfering messages that come on to the page  There are multiple frames on the page which communicate with the page using window message event and object  few of them can be third party services like cookieq for managing cookies  or may be cartwire an e-com integration service   You need to handle the onmessage event to check from where the messages are coming  and then parse the JSON accordingly   I faced a similar problem  where one of the integration was passing a JSON object and other was passing a string starting with u

[javascript] Uncaught SyntaxError: Unexpected token u in JSON at position 0

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