How do I turn data into JSON and pass it to the backend through Ajax

Thank you for your view. For example, when a user logs in, he / she transfers the account password to the background through JSON format. How to implement it through post? I tried to put the JSON format {Username: username, phone: Phone} into data, but the background didn't receive it. At present, I can only splice the value behind the website. Is it my writing problem, or is there any other way?

Thank you very much for your help, which has solved my big problem. I tried character splicing before, but it failed.

I tried to use the JSON method to pass values, and found that the value must be added "" to take effect, otherwise it will be null. So I created ll and RR to represent "and". Then I spliced them together to display them normally. I don't know if it's caused by my wrong use. Please be able to answer my doubts. Thank you

When I don't add "", I can't put the value in JSON. The displayed value is null.

I don't know what you are doing wrong. Simply setting JSON key "name" to TextBox.text works for me, the resulting compact string looks like this:

{"name":"John"}

I don't know what the problem is. I used the 180beta version! Is it related to the region? I'm from China.