Flask: python object to json triggering error when read by javascript

Question

I'm trying to pass python dictionaries and javascript objects back and forth as necessary. From similar questions, I've gathered that I need to do this.

Python:

posts = [
{'author':'JL Rowling','title':'Harry Potter'},
{'author':'JRR Tolkien','title':'Lord of the Rings'},
]

Javascript:

var jsonPosts = JSON.parse({{ posts }});
console.log(jsonPosts);

Likewise, these doesn't work either:

var jsonPosts = JSON.parse(posts|tojson);
var jsonPosts = {{ posts|tojson }};

The JS error I'm triggering is TypeError: Object of type Undefined is not JSON serializable

I got this advice from the following Q/A:

Python to Javascript JSON objects (Flask)

How can I pass data from Flask to JavaScript in a template?

How can I fix this?

Edit: I've used answer recommendation and found the following error to be present in the console:

VM129:1 Uncaught SyntaxError: Unexpected token u in JSON at position 0
    at JSON.parse (<anonymous>)
    at about:16

Corresponding to

let jsonPosts = JSON.parse();

It seems that it doesn't have access to encoded_posts.

Jim Wright · Accepted Answer · 2020-05-25 19:25:23Z

0

You need to use the encoded posts:

encoded_posts = json.dumps(posts)

That will give you string, which is what JSON.parse is expecting.

var jsonPosts = JSON.parse({{ encoded_posts }});

answered May 25, 2020 at 19:25

Jim Wright

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1 Comment

jbuddy_13 Over a year ago

I tried this to no success. So I troubleshooted the JSON and the issue seems to be there.

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