const obj = {a:10,b:{c:[20,30,40],d:{e:50,f:60}}}

function deelpCloneObject(obj) {
    if(obj === null || typeof obj !== "object"){
        return obj
    }
    if(Array.isArray(obj)){
        const copyArr = []
        for(let value of obj){
            copyArr.push(deelpCloneObject(value))
        }
        return copyArr
    }
    const cloneObj = {}
    for(let [key, value] of Object.entries(obj)){
        cloneObj[key] = deelpCloneObject(value)
    }
    return cloneObj
}

const deepCopyOfobj = deelpCloneObject(obj) 
deepCopyOfobj.b.d.f = ["string1"]
console.log(deepCopyOfobj)
console.log(obj)