const target = {
a: {
b: {
c: {
d: 1
}
},
e: 5,
f: 6,
h: 10
}
}
const source = {
a: {
b: {
c: {
d: 1
}
},
e: 2,
f: 3
}
}
Object.assign(target, source)
console.log(target)