Ashrafpoless: inside-js, 3 weeks

[Ashrafpoless]

Inside JS

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Learning Objectives

Priorities: 🥚, 🐣, 🐥, 🐔 (click to learn more)

There is a lot to learn in this repository. If you can't master all the material
at once, that's expected! Anything you don't master now will always be waiting
for you to review when you need it. These 4 emoji's will help you prioritize
your study time and to measure your progress:

• 🥚: Understanding this material is required, it covers the base skills you'll
  need to move on. You do not need to finish all of them but should feel
  comfortable that you could with enough time.
• 🐣: You have started all of these exercises and feel you could complete them
  all if you just had more time. It may not be easy for you but with effort you
  can make it through.
• 🐥: You have studied the examples and started some exercises if you had time.
  You should have a big-picture understanding of these concepts/skills, but may
  not be confident completing the exercises.
• 🐔: These concepts or skills are not necessary but are related to this module.
  If you are finished with 🥚, 🐣 and 🐥 you can use the 🐔 exercises to push
  yourself without getting distracted from the module's main objectives.

---

0. Asserting

• Skills:
  • 🥚 Predicting Execution: You can use the browser's debugger to step
    through your code. Before each step you can make a prediction about what
    will happen, after each step you can check your prediction.
  • 🥚 Assertion Testing: You can write assertion tests to predict what
    values will be in your program at a specific step of execution.
• Language Features
  • 🥚 Comments: You can write clear, helpful comments and can explain
    different ways comments can be used in a program.
  • 🥚 Strings: You can write and read string values in a program.
  • 🥚 let vs. const: You can explain the differences between let
    and const including: uninitialized declarations and reassignment.
    You can determine when a variable can be assigned with const in a
    program.
  • 🥚 Strict Comparison: You can explain how the === and !==
    operators compare strings, and can predict the result of any string
    comparison.
  • 🥚 console.log: You can use console.log to create program traces
    in the console, and to print other helpful info for developers.
  • 🥚 console.assert: You can use the console.assert for assertion
    testing, and can write a helpful message assertion message.

1. Primitives and Operators

• Skills:
  • 🥚 Predicting Truthiness: You can predict the truthiness of any
    primitive value.
  • 🐣 Tracing Operators: You can use an operators trace table to
    evaluate expressions with more than one operator, and you can check your
    work with the [trace] button.
• Language Features
  • 🥚 Primitive Types: You can explain the difference between the 5
    main primitive types (string, number, boolean, null,
    undefined) and what they are used for in a program.
  • 🥚 typeof: You can predict the typeof operator's output for
    values from any of the 5 main primitive types.
  • 🥚 Explicit Coercion: You can predict & check the outputs when using
    Boolean(), String() and Number() to convert between primitive
    types.
  • 🥚 Truthiness Operators: You can explain how truthiness is used
    when evaluating &&, ||, ! and ? :.
  • 🐣 Short-Circuiting: You can write an example that demonstrates how
    short-circuiting works with && and ||.
  • Implicit Coercion:
    • 🐣 You can explain what implicit coercion is and how it can cause
      problems in your programs.
    • 🐣 You can explain the rules for implicit coercion in common operators
      such as +, ! and >.
  • 🐣 Comparisons: You can predict and check the result of any
    primitive comparison.
  • 🐣 Template Literals: You can read and trace multi-line template
    literal strings.
  • 🐥 Statements vs. Expressions: You can identify if a piece of code
    is a statement or an expression.
  • 🐔 Arithmetic: You can use JavaScript to do math, and can explain or
    debug your expressions when they evaluate to something unexpected.

2. Control Flow

• Skills:
  • 🥚 Imperative Programming: You can define the imperative
    programming paradigm and can explain how you know the programs in this
    chapter are imperative.
  • Writing Interactive Programs: For programs that take a string from
    users:
    • 🥚 Blanks: You can complete a program by filling in the blanks.
    • 🐣 Bugs: You can fix bugs in an otherwise complete program.
    • 🐣 Goals: You can write the missing portion of a program.
    • 🐔 Empty Page: You can develop a program with specific behavior
      starting from an empty page.
  • 🐥 User Numbers: You can complete, debug and write programs that
    cast user input from string to number.
  • 🐥 Stateful Programs: You can step through, debug and complete
    programs with an HTML/CSS interface that store user data in a variable
    between interactions.
  • Refactoring Control Flow:
    • 🐥 Conditionals: You can refactor between truthiness operators and
      if/else statements.
    • 🐥 Loops: You can either refactor between all loop types, or
      explain when it is not possible (or a good idea).
• Language Features: You are comfortable reading and tracing programs that
  use ...
  • 🥚 Block Scope: You can show how block scope works using code
    snippets and your browser's debugger.
  • 🥚 Conditionals: You can predict and trace a program's path through
    conditional statements.
  • 🥚 While Loops: You can predict and trace simple programs that use
    while loops.
  • 🥚 for-of Strings: You can predict and trace simple programs that
    iterate through the characters of a string using for-of.
  • 🥚 For Loops: You can explain how a for loops works by refactoring
    simple for loops into while loops.
  • 🐣 Break: You can predict and trace simple programs that use
    break.
  • 🐣 Continue: You can predict and trace simple programs that use
    continue.

3. Functions

• Skills:
  • 🥚 Tracing: You can use the debugger to predict and check the
    execution of small programs that use functions. This includes:
  • 🥚 Test Cases: You can explain a simple function's behavior using
    inputs & outputs.
  • 🐣 Documenting Functions: You can write a JS Doc comment to describe
    a function's behavior, inputs and outputs.
• Language Features:
  • 🥚 ES6 Arrow Functions:
    • Defining a Function: You can show where a function is defined in a
      program.
    • Parameters: You can find a function's parameters in it's definition
    • Return Statement: You can find the return statements in a function's
      definition.
    • Calling a Function: You can show where a function called in a
      program
    • Arguments: You can show the arguments passed to a function call.
    • Return Value: You can show how a function's return value is used
      after the function call.
  • 🥚 Default Parameters: You can explain how default parameters work,
    and how they help a developer read/understand a function definition.
  • 🐣 The Callstack: You can explain and inspect the callstack using
    the browser's debugger.
  • 🐥 Variables in Functions: You can explain three different ways a
    variable in a function can be declared/assigned, and can show this in
    the debugger:
    1. Parameters: A parameter is assigned it's value when a function is
       called with arguments.
    2. Local Variables: A variable declared in the function's curly braces.
    3. Parent Scope Variables: A variable that was declared outside of the
       function but used inside the function (avoid this for now.)

5. Unit Testing

• Skills:
  • 🥚 Testing Environments: You understand that the conventional
    describe/it/expect.toEqual functions are defined by a testing
    library and made available as global variables in a testing
    environment. They are not part of JavaScript!
  • 🥚 File Sub-Extensions: You can identify how a file is used by it
    sub-extension: file.__.js. Sub-extensions are a convention for
    developers and development tools. They do not change how JavaScript
    inside the file works.
  • 🥚 Reading Tests: You can read unit tests to understand what a
    function is supposed to do.
  • 🥚 Stepping Through Tests: You can step through unit tests in the
    debugger, stepping over the global testing functions and into the
    function you are testing.
  • 🐣 Writing Tests: Given a working function, you can write passing
    unit tests to describe it's behavior.
  • 🐣 Debugging Functions: Given working tests and a function with
    small mistakes, you can use the tests as a guide while debugging the
    function.
  • 🐥 Passing Tests: Given working unit tests and an empty function,
    you can write code to pass the tests.
• Language Features:
  • nothing new here!

6. ES Modules

• Skills:
  • 🥚 Spec Files: You can work with functions and unit tests separated
    into two files.
  • 🥚 Visualizing Dependencies: You can use the
    VSCode Dependency Cruiser extension
    and the ?deps lens to visualize the dependencies in a folder.
  • 🐣 Refactoring Tests: You can refactor a function and unit tests
    from one file to two files: one with the function, one with the unit
    tests.
• Language Features:
  • 🥚 Module Files: Are always in strict mode by default, no more
    'use strict'!
  • 🥚 Named Exports: You can export a variable and it's value using
    export const _ = () => {};
  • 🥚 Named Imports: You can import a variable and it's value from
    another file using import { _ } from './path/to/file.js';
  • 🐥 Module Life-Cycle: You understand that ES Modules are static,
    and are evaluated at creation phase.

6. Using Functions

• Skills:
  • 🥚 Procedural Programming: You can define the procedural
    programming paradigm and can explain how you know the programs in this
    chapter are procedural.
  • 🥚 Using Functions: You can use a pre-written functions in a
    program.
  • 🐣 Writing Functions: You can write functions that are used in a
    program.
  • 🐥 Refactoring Functions: You can refactor a function out of a
    program and test the function separately.
  • 🐔 Reverse-Engineering: You can reverse-engineer an example program
    and refactor parts of your program into separate functions.
• Language Features:
  • Nothing new here!

7. Arrays

• Skills:
  • 🥚 Reference vs. Value: You can explain how arrays are stored in
    memory and can demonstrate using examples run in JS Tutor.
  • 🥚 Deep vs. Shallow Comparison: You can explain use the concept of
    reference vs. value to explain how a deep comparison is different than a
    shallow comparison.
  • Side-Effects: You can ...
    • 🥚 Explain what side-effects are with an example.
    • 🥚 Avoid side effects when writing your own functions.
    • 🐣 Write tests to check if a function has side-effects.
    • 🐣 Fix side-effects in buggy functions.
  • Integrating Arrays: You can work with programs that use arrays to store
    user data:
    • 🥚 Call: You can call pre-written functions in a program:
    • 🐣 Write: You can write functions that are used in a pre-written
      program.
    • 🐣 Refactor: You can refactor logic from a program into a separate
      function. You can avoid side-effects and test your function.
    • 🐔 Reverse-Engineer: You can reverse-engineer a program,
      refactoring logic to a separate function if necessary.
  • 🐥 Stateful Programs: You can step through, debug and complete
    programs with an HTML/CSS interface that store user data in an array between
    interactions.
• Language Features: You are comfortable reading and tracing programs that
  use ...
  • 🥚 Array Literals: You can create a new array in your program with
    initial values using the array literal syntax:
    const arr = ['items'];
  • 🥚 Adding and Removing Items: You can use these methods to add and
    remove items in an array:
    • arr.push(): Adds a new item to the end of an array.
    • arr.pop(): Removes the last item in an array.
    • arr.shift(): Adds a new item to the front of an array.
    • arr.unshift(): Removes the first item in an array.
  • 🥚 Reading Items: You can read items in an array using:
    • arr[i]: Access a specific item in an array using square brackets a
      positive index.
    • arr.at(i): Access a specific item in an array using .at() and a
      positive or negative index.
  • 🥚 Updating Items: You can update any item in an array using it's
    index, square brackets and assignments: arr[4] = 'hello'.
  • 🥚 Iterating Over Arrays:
    • for (const item of arr): You use for-of loops to iterate
      forwards through an array.
    • for (let i = ...): You can use for loops to iterate forwards and
      backwards through an array.
  • 🥚 Array.isArray(): You can use Array.isArray() to check if
    something is an array: Array.isArray(something)
  • 🥚 Spread Syntax: you can use spread syntax to create a shallow
    copy of an array: const shallowCopy = [...arr];

8. Functional Array Methods

• Skills:
  • 🥚 Declarative Programming: You can define the declarative
    programming paradigm and can explain how you know that code using
    functional array methods is declarative.
  • 🥚 Array Strategies: You can explain these array strategies using a
    diagram or drawing:
    • Mapping: Modifying each item in an array and putting the results
      in a new array.
    • Filtering: Creating a new array with only the items from the old
      array that match some criteria.
    • Every Item: Checking if every item in an array matches some
      criteria.
    • Some Items: Checking if at least one item in an array matches some
      criteria.
    • Finding: Finding the first item in an array that matches some
      criteria.
    • Reducing: Combining all the items in an array to create a single
      result.
  • 🐣 Using Callbacks: You can explain what a callback is, and can ...
    • Pass a callback into a higher-order function that consumes it.
    • Write a callback for a higher-order function to consume.
    • Consume callbacks in a higher-order function that you write.
    • Decide when to declare callbacks inline, and when to declare them
      separately.
  • 🐣 Debugging Functional Array Methods: You can step through code
    that uses functional array methods in your debugger, and can use the
    scopes panel to explain what is happening behind the scenes.
• Language Features:
  • Array Methods: You can read and trace code that uses these array
    methods, you can also use them to solve simple coding challenges:
    • 🥚 [].every
    • 🥚 [].some
    • 🐣 [].map
    • 🐣 [].filter
    • 🐣 [].find
    • 🐥 [].reduce
  • 🐣 Higher-Order Functions: You can explain what a higher order
    function is using a simple example.
  • 🐥 Implicit Returns: You understand when a function can be written
    with an implicit return and can decide if it makes your code more or
    less readable.

9. Multiple Interactions

• Skills:
  • 🥚 Avoiding Side Effects: You can read, debug and write functions
    that use objects as arguments, without creating side-effects.
  • 🐣 Stateful Programs: You can step through, debug and complete
    programs with an HTML/CSS interface that store user data in an object
    between interactions.
• Language Features:
  • 🥚 Object Literals: You can declare a new object with initial
    key/value pairs using object literal syntax:
    const obj = { a: 1, b: 2 };.
  • 🐣 Dots vs. Brackets: You can explain the difference between dot
    and bracket access in an object and can decide which one is best in
    your code.
  • 🐣 Reference vs. Values: You can show that objects are stored by
    reference with an example that modifies one object from two variables.