Flask-CORS
When I set up a server with Flask to experiment with experimental functions, the server's API is blocked by the CORS policy when I try to read the JS of the content placed on another server.
code::
Access to fetch at 'http://localhost:5000/api/' from origin 'http://localhost:3000' has been blocked by CORS policy: Response to preflight request doesn't pass access control check: No 'Access-Control-Allow-Origin' header is present on the requested resource. If an opaque response serves your needs, set the request's mode to 'no-cors' to fetch the resource with CORS disabled.
server-side
Use Flask-CORS (pip install -U flask-cors)
https://flask-cors.readthedocs.io/en/latest/
code:diff
from flask import Flask
+ from flask_cors import CORS
app = Flask(__name__)
+ CORS(app)
client-side
code:diff
fetch("http://localhost:5000/api/", {
+ mode: "cors",
method: "POST",
body: JSON.stringify(data),
headers: {
"Content-Type": "application/json",
},
}).then((response) => {
Flask receives the data as json since it is hit with "Content-Type": "application/json".
I forgot to do this and got a 400 Bad Request.
400 Bad Request by hitting Flask from JS
preflight request is 308 Permanent Redirect in OPTIONS
Caused by trailing slash
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