Issue sorting by date with lodash

Hi everybody, I'm trying to have a sorted list of items by data using lodash and vue moments, I'm using a computed property but for some reason this computed property named sortByUsedDate returns a number instead of a sorted array... it's returning 11 exactly.

This is my code:

sortByUsedDate: function(){

        let sortedCodes = _.orderBy(this.modalPayload.discountcodes, (code) => {
            return Vue.moment(code.usedDate).format('MDYYYY');
        }, ['desc']);

        let sortedWithoutUnused = _.remove(sortedCodes, function(code) {
            return code.isBought === 1;
        });

        let unusedCodes = _.filter(this.modalPayload.discountcodes, function(code){
            return code.isBought == 0;
        });

        let final = sortedWithoutUnused.push(unusedCodes);

        return final;
    }