proposal: add selectedfilters getter to the FilterManager

[Youhan]

I thought it would be nice to add this feature to the filter manager to keep track of selected filters.

One use case is to be able to add a list of selected filters somewhere on the page.
It could also be used to refactor some other methods that are doing calculations to see which filters are selected.

I am doing it this way, as a sample

// add a getter method for selected filters to manager prototype
Object.defineProperty(manager, 'selectedFilters', {
    get: function() {
        const selectedFilters = [];
        this.filters.forEach(filter => {
            if (
                FilterManager.isKlevuFilterResultOptions(filter) ||
                FilterManager.isKlevuFilterResultRating(filter)
            ) {
                const selected = filter.options.filter(
                    subOption => subOption.selected === true
                );
                if (selected.length === 0) {
                    return;
                }
                for (const option of selected) {
                    selectedFilters.push({
                        key: filter.key,
                        label: filter.label,
                        type: filter.type,
                        value: option.value,
                    });
                }
            }
            else if (FilterManager.isKlevuFilterResultSlider(filter)) {
                if (!filter.start || !filter.end) {
                    return;
                }
                selectedFilters.push({
                    key: filter.key,
                    label: filter.label,
                    type: filter.type,
                    value: `${filter.start}-${filter.end}`
                });
            }
        });

        return selectedFilters;
    }
});

Then we can use it like

const manager = new FilterManager()
console.log(manager.selectedFilters)

[rallu]

Looks excellent and very handy! Would you have time to create a PR our of this? You would get your name in the credits... :)

Here is the filterManager to add it to: https://github.com/klevultd/frontend-sdk/blob/master/packages/klevu-core/src/store/filterManager.ts