[Vuejs]-Passing a variable to child component in Vue.js

You possibly seem to have a wrong reference to this. In JavaScript context, this refers to the immediate context, but Vue props are tied to the context of the class/component.

To prevent this, store the reference of this to another variable, or use an arrow function

methods: {
            logThis: () => {
                console.log(this.subscription);
            },
        }