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js-data-structures-objects-lab's Introduction

Objects Lab

Problem Statement

We covered the concepts of Objects in JavaScript. Now it's time to put the concepts into practice.

Learning Goals

Create Objects
Perform operations on Objects

Instructions

Follow the steps below, running learn as you go to get additional information from the tests. To start, define a driver variable and assign it to an Object. Various updates will be applied to this variable (destructively and non-destructively) in this lab.

You'll be writing four functions:

updateDriverWithKeyAndValue()- this function should take in three arguments: a driver Object, a key and a value. This function should not mutate the driver and should return a new driver that has an updated value for the key passed in.
destructivelyUpdateDriverWithKeyAndValue() - this function should work the same as updateDriverWithKeyAndValue() but it should mutate the driver parameter passed in.
deleteFromDriverByKey() - this function should take in a driver Object and a key. It should delete the key/value pair for the key that was passed in from the driver Object. This should all not actually mutate the driver passed in.
destructivelyDeleteFromDriverByKey() - this function should work the same as deleteFromDriverByKey() but it should mutate the driver passed in. Be sure to consider whether and how using dot notation vs. bracket notation might affect your solution.

HINT: You might find deleteFromDriverByKey() to be a bit hard to write non-destructively. Think about how we learned to use Object.assign(). What happens if we do this:

const obj = { foo: "bar" };

const newObj = Object.assign({}, obj);

newObj;
// => { foo: "bar" }

delete newObj['foo'];
// => true

newObj;
// => {}

obj;
// => { foo: "bar" }

Something to keep in mind!

Conclusion

In this lab, we worked with creating Objects and performing operations on them.

Resources

MDN: Object

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js-data-structures-objects-lab's Issues

KNOWN ISSUE: so return NaN passes the deleteFromDriverByKey test?

function deleteFromDriverByKey(driver, key){
  return NaN 
}
// why does this pass the test

This is what I actually tried and it passed the test just fine without me realizing that it was actually returning NaN

function deleteFromDriverByKey(driver, key){
  return driver - driver[key]  // NaN 
}

Only when I went to the next function and tried a similar answer which didn't work did I open up the debugger and realize that it was returning NaN

function destructivelyDeleteFromDriverByKey(driver, key){
  driver -= key
  return driver
}

clarification for readme:

I'm guessing that this:

The function should not mutate the driver parameter and return a new driver that has an updated value for the key passed in.

means:

The function should not mutate the driver parameter and should return a new driver that has an updated value for the key passed in.

typo in indexTest.js, line 17

an driver should be a driver
original should be original

it('returns an driver with the orignal key value pairs and the new key value pair', function () {
  expect(updateDriverWithKeyAndValue(driver, 'address', '11 Broadway')).to.eql({
    name: 'Sam',
    address: '11 Broadway'
  });
});

Package.json index.html and sinon-utils

Can you update the scripts in the packag.json, update the index.html to work and remove the sinon-utils file?

Typo

I think there is a typo in the test. It says to call a function - "destructivelyDeleteFromdriverByKey" but it really means "destructivelyDeleteFromDriverByKey". The D in driver should be capitalized. The function needs to have the capital D to pass the test.

please clarify readme

pls drop a hint in the readme re:

You can't pass this test with spread operator! You must use Object.assign({},driver).
you cannot use dot syntax for deleting key , you MUST use brackets.

the last test name is different when you run learn

the 'd' in driver is listed as destructivelyDeleteFromdriverByKey in the test
not destructivelyDeleteFromDriverByKey

Lab is not aware of local tests

Before all hook timeout preventing all tests from being run (Mocha)

"before all" hook

0 passing (3s)
1 failing

"before all" hook:
Error: Timeout of 2000ms exceeded. For async tests and hooks, ensure "done()" is called; if returning a Promise, ensure it resolves.
at Object.done (node_modules/mocha-jsdom/index.js:70:7)
at /Users/Mackenzie/js-data-structures-objects-lab-online-web-sp-000/node_modules/jsdom/lib/jsdom.js:325:18
at processTicksAndRejections (internal/process/task_queues.js:82:9)

Not loading or passing given despite tests passing

Function names

The function names in test/indexTest.js do not match the names given on localhost:8000 when "learn" is run

KNOWN ISSUES

Problem: so return NaN passes the deleteFromDriverByKey test?
#10
Notify: @ arye-dov-eidelman

Capital D missing from destructivelyDeleteFromDriverByKey()

The capital D of ...Driver... is missing from two instances of destructivelyDeleteFromdriverByKey. Added the code from IndexTest.js:

    it('returns driver without the delete key/value pair', function () {
      let newdriver = **destructivelyDeleteFromdriverByKey**(driver, 'name');

      expect(newdriver['name']).to.equal(undefined);
    });

    it('modifies the original driver', function () {
      let newdriver = destructivelyDeleteFromDriverByKey(driver, 'name');

      expect(driver['name']).to.equal(undefined);```

Hint for the lab gives wrong format

The hint for the lab uses dot notation to reference the key, as well as the lesson before this teaching us how to non destructively use delete to remove a key. Using dot notation only satisfies one of the test conditions so when calling delete newObj.key it still fails for "1) deletes key from a clone of driver and returns the new driver (it is non-destructive)", only when using bracket notation does it actually satisfy the test. If this is intentional my apologies, but it seemed to me from the hint that dot notation is what is expected or at least suggested.

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