SOURCE

const target = {
    field1: 1,
    field2: undefined,
    field3: 'ConardLi',
    field4: {
        child: 'child',
        child2: {
            child2: 'child2'
        }
    },
    field5: null,
    field6: [1, 2, 3, 4],
};
target.field7 = target;
const isObject = (val) => (typeof val === 'object' || typeof val === 'function') && val !== null
const deepClone = (target, map = new Map()) => {
    if (isObject(target)) {
        let targetCloned = Array.isArray(target) ? [] : {};
        if (map.get(target)) {
            return map.get(target);
        }
        map.set(target, targetCloned);
        for (key in target) {
            targetCloned[key] = deepClone(target[key], map);
        }
        return targetCloned;
    } else {
        return target;
    }
    return targetCloned;
}



const newVal = deepClone(target);
newVal.field1 = 2;
newVal.field6.push(5);
console.log(newVal)
console.log('111')
console.log(target)