strawmen.js

const h1 = {
  a: { 
    b: {
      c: {
        foo: "bar"
      }
    }
  }
}

// we want to change foo to "baz"

const h2 = Object.assign({}, h1, {
  a: Object.assign({}, h1.a, {
    b: Object.assign({}, h1.b, {
      c: Object.assign({}, h1.c, {
        foo: "baz"
      })
    })
  })
})

// vs 

const m1 = Immutable.Map(h1)
const m2 = m1.setIn(['a', 'b', 'c'], "baz");

// and similarly with arrays
// let's say we want to increment h1.a.b.c[2]

const h1 = {
  a: {
    b: {
      c: [1, 2, 3, 4, 5]
    }
  }
}

const a2 = h2.a.b.c.slice();
a2[2] += 1;

const h2 = Object.assign({}, h1, {
  a: Object.assign({}, h1.a, {
    b: Object.assign({}, h1.b, {
      c: a2  
    })
  })
})

// vs

const m1 = Immutable.Map(h2)
const m2 = m1.updateIn(['a', 'b', 'c', 2], (n) => { return n + 1 })