How to change variable in data from mounted to promise?

Question

Vue.js

Hello, tell me why in the mounted or created hook from promise->then it is not possible to change the variable in data, example:

data(){
    return {
        foo: null
    }
},
created(){
    this.foo = "baR"
    this.$http.get("server.api").then( () => {
        this.foo = "baZ" 
    })
    console.log(this.foo) // -> "baR"
}

Even if you bind the context, the result is the same