Resolve/Reject Promises externally

promise-helper.js

let contexts = {}

function getContext(key) {
    if (typeof contexts[key] === 'undefined') {
        contexts[key] = { promise: null, resolve: null, reject: null }
    }
    return contexts[key]
}

function getPromise(key) {
    let context = getContext(key)
    if (context.promise === null) {
        context.promise = new Promise((resolve, reject) => {
            context.resolve = resolve
            context.reject = reject
        })
    }
    return context.promise
}

function resolvePromise(key, value) {
    sealPromise(key, true, value)
}

function rejectPromise(key, error) {
    sealPromise(key, false, error)
}

function sealPromise(key, resolve_or_reject, result) {
    let context = getContext(key)
    if (context.promise !== null) {
        if (resolve_or_reject) {
            context.resolve(result)
        } else {
            context.reject(result)
        }
        context.promise = null
        context.resolve = null
        context.reject = null
    }
}

Sample usage:

    userSignInShow ({ commit }) {
        commit('USER_SET_SHOW_SIGN_IN', true)
        return getPromise('userSignIn')
    },

    userSignInHide ({ commit, getters }) {
        commit('USER_SET_SHOW_SIGN_IN', false)
        if (getters.userLoggedIn) {
            resolvePromise('userSignIn', true)
        } else {
            rejectPromise('userSignIn', new Error('Not logged in'))
        }
    },

A few words about the context here: after a Modal for login is shown, the actual login may happen or fail by many different reasons, in many different ways... there is traditional user/pass, there is social login (oAuth - in distinct window), there is the sign up form... it is only when the modal is closed (be it by user hitting close button, or any other way) that the actual login state is consulted, providing the resolved/rejected state for the component which triggered the Modal display.