Vuejs – call computed function from javascript defined in another computed function

I have this computed function defined in a standalone Vue component

watchForCustomer() {
  this.customerId = window.meta.page.customerId
  if(this.customerId) {
    $(document).on("click", function(element) {
      let checkout = ['checkout'].includes(element.currentTarget.activeElement.name)
      if(checkout) {
        let checkoutForm = ['checkout', 'cart'].includes(element.currentTarget.activeElement.form.action.split('/').at(-1))
        if(checkoutForm) {
          getCustomerCredit()
        }
      }
    })
  }
},

The problem is that getCustomerCredit() is not getting called.

I’ve tried to define it as:
this.getCustomerCredit
getCustomerCredit()
app.$options.getCustomerCredit()

and I get either that the function is not defined or it simply doesn’t call it.

So how can I call this getcustomerCredit inside the document on click event?