MKLNKs / js_stateful-clones

Cloning and transforming state

Read the guideline before start

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Task description

Write a function transformStateWithClones that take a state object and an actions array and return an array of the same length as actions containing all previous versions of the state. Each element of the resulting array has to represent the state produced by the next operation.

IMPORTANT! You must not modify the initial state object in any way!

• state is an initial object. It should always remain the same.

• actions is an array of objects. Each object in this array has the next properties:

  • type contains a string: either 'addProperties', 'removeProperties' or 'clear';
  • The second property of each object depends on type and may be one of the following:
    • if type is addProperties, the second property is extraData. It contains an object with key: value pairs to add to the state;
    • if type is removeProperties, the second property is keysToRemove. It contains an array with the list of property names (keys) to remove from the state; (Not existing properties should be ignored)
    • if type is clear you should create an empty state object. No second property in this case;

Example of usage:

If state is {foo: 'bar', bar: 'foo'}, then

transformStateWithClones(state, [
  {type: 'addProperties', extraData: {name: 'Jim', hello: 'world'}},
  {type: 'removeProperties', keysToRemove: ['bar', 'hello']},
  {type: 'addProperties', extraData: {another: 'one'}}
])

must return the following array:

[
  {foo: 'bar', bar: 'foo', name: 'Jim', hello: 'world'},
  {foo: 'bar', name: 'Jim'},
  {foo: 'bar', name: 'Jim', another: 'one'}
].

The state object itself should not be modified and must remain {foo: 'bar', bar: 'foo'}.

Then after calling

transformStateWithClones(state, [
  {type: 'addProperties', extraData: {yet: 'another property'}}
  {type: 'clear'},
  {type: 'addProperties', extraData: {foo: 'bar', name: 'Jim'}}
])

we must get

[
  {foo: 'bar', bar: 'foo', yet: 'another property'},
  {},
  {foo: 'bar', name: 'Jim'}
].

the state variable must still contain {foo: 'bar', bar: 'foo'}.