Consider this simple JavaScript data structure (the "content") which consists of an array of objects. Each object has an "id" property. For example:

[{ "id": "cat" }, { "id": "frog" }, { "id": "dog" }, { "id": "horse" }, { "id": "caribou" } ]

The ids in an instance of the "content" data structure are unique (and must remain so). For example, it would be an error to attempt to add a new object to the above array with an "id" of "cat".

A simple language is used to describe transformations which can be applied to the "content" data structure described above. Each transformation is an object with properties that describe how the content should be transformed. All transforms contain two common properties; "type" and "target". The "type" property determines the type of transformation to be performed. The "target" property determines the object in the data array to be transformed. An example transform is below:

{ "type":"remove", "target": { "id": "cat" } }

The target of a transform may be identified by its "id" (as above), or by its position in the array (zero-based). An example of this is below:

{ "type":"move", "target": { "pos": "0" }, "distance": 2 }

This transformation attempts to move the first item in the array forward by a distance of two places (so it will now be in third position in the array). If the distance would place the moved item outside the bounds of the array, then the move should "wrap around". For example, moving the first item in the array by a distance of -1 should place the item at the end of the array.

There are three types of transformation:

1. Remove

Delete the item identified by its "id" from the "data" array. See the examples below:

{ "type":"remove", "target": { "id": "cat" } }

2. Rename

Rename the item identified by its "id" to the value specified in the "newid" property.

{ "type":"rename", "target": { "id": "horse" }, "newid":"lion" }

3. Move

Move the item identified by its current position forwards or backwards through the array by the specified distance (negative distance indicate moving backwards, positive distance indicates moving forward).

{ "type":"move", "target": { "pos": 2 }, "distance":-1 }

{ "type":"move", "target": { "pos": 0 }, "distance":2 }

An array of transformations can be applied to content by iterating over the array and applying each transformation in order. Each transform should be applied only if it is "possible". If a transform cannot be applied, it should be ignored and the next transform should be processed. The list below specifies the situations in which each type of transformation should be ignored:

• Remove should be ignored if:
  • no object with the specified id exists
• Rename should be ignored if:
  • no object with the specified id exists
  • another object exists with the same id as "newid"
• Move should be ignored if:
  • the specified position is outside of the bounds of the array

Implement (and test) a JavaScript function called transform which takes a content array and a transformations array as parameters and returns the transformed content array. Your solution should take into account performance as well as good style and correctness. You may create helper functions and additional data structures in your implementation if you find them useful, but the transform function must return a valid content array as described above. You should be prepared to discuss your design in our next interview.

The function prototype and sample usage is supplied below:

function transform(content, transformations) { //To be implemented }

let content = { /_ .../ }; let trans = = { / ..._/ };

let result = transform(content, trans);

An example content and a transformation list are provided for testing. You should create your own additional content and transformation lists to support you development and testing needs. You should pay attention to the correctness and performance of your solution, and also consider the most appropriate way to present a visualisation of the pre- and post- state of the data, and provide users with a way to see how their transformation task has executed.