Auto generating API keys using the Application Authentication Endpoint

I am trying to auto generate API keys from a woocommerce website , but I am getting an error like this :

name:"FetchError"
message:"invalid json response body at https:/...............
.............................reason: Unexpected token < in JSON at position 0"
type:"invalid-json"

this is the code I have used , i have changed website names to sample names :



????????const?store_url?=?'https://sample.com/';
????????const?endpoint?=?'wc-auth/v1/authorize';
????????const?query_string?=?new?URLSearchParams([
????????????['app_name',?'MyShoppingWebsite'],
????????????['scope',?'read_write'],
????????????['user_id',?'123'],
????????????['return_url',?'https://example.com/apipractice'],
????????????['callback_url',?'https://example.com/apipractice']
????????]).toString();

????????const?url?=?store_url?+?endpoint?+?'?'?+?query_string;



this is run from another website . 
any help is appreciated , thank you !!