How to change the value of a variable in vue js depending on the URL?

Question

Vue.js

Hello everyone, can you please tell me how to change the data in a variable depending on the URL?
That is, if the address is: site.com in the {{ price }} variable, output 100
If the address is site.com?promo=50% , output 50 in the variable

Answer 1

https://codesandbox.io/s/qna-q952763-1d7b6