A function that deletes empty object properties (null or undefined) and also deletes empty objects recursively. It is a small modification from https://stackoverflow.com/a/42736367/1734815

clearEmpties.js

function valid(x){
    return !( x == null || Number.isNaN(x));
}
function clearEmpties(o) {
    for (const k in o) {
        if (!valid(o[k])) {
            delete o[k];
            continue;
        }
        if (typeof o[k] !== 'object') {
            continue;
        }

        clearEmpties( o[ k ] );
        if (Array.isArray(o[k])){
            o[k] = o[k].filter(valid);
        }
        if (Object.keys(o[k]).length === 0) {
            delete o[k];
        }
    }
    return o;
}

/** =========================     EXAMPLES     ========================= **/
const dirty = {
    key1: 'AAA',
    key2: {
        key21: 'BBB'
    },
    key3: {
        key31: true,
        key32: false
    },
    key4: {
        key41: undefined,
        key42: null,
        key43: [],
        key44: {},
        key45: {
          key451: NaN,
          key452: {
            key4521: {}
        },
          key453: [{ foo: {}, bar:'' }, NaN, null, undefined]
      },
        key46: ''
    },
    key5: {
        key51: 1,
        key52: '  ',
        key53: [1, '2', {}, []],
        key54: [{ foo: { bar: true, baz: null } }, { foo: { bar: '', baz: 0 } }]
    },
    key6: function () {}
};

const object = {
    a: {
        b: 1,
        c: {
            a: 1,
            d: {},
            e: { // will need to be removed after f has been removed
                f: {},
                z: {
                    w: null
                },
                y: []
            }
        }
    },

    b: {}
};

console.log(JSON.stringify(clearEmpties(object),null,2));
console.log(JSON.stringify(clearEmpties(dirty),null,2));