JSFiddle - React, Tailwind, and code Playground

JavaScript

obj = { x:555, y: "hi" }
obj.myself = obj

seen = []

json = JSON.stringify(obj, function(key, val) {
   if (typeof val == "object") {
        if (seen.indexOf(val) >= 0)
            return
        seen.push(val)
    }
    return val
})

alert(json)