JavaScript Competency

  • 21m
  • 21 questions
The JavaScript Competency benchmark assesses your knowledge of creating and managing objects in JavaScript using the built-in tools available. You will be evaluated on your skills in recognizing functions as arguments to other functions and as return values of functions, and linking functions with specific objects when invoked. A learner who scores high on this benchmark demonstrates that they have the skills to use array of features and a variety of functions offered in JavaScript.

Topics covered

  • assign a function to a variable and pass a function as an argument to another function
  • break down and access the components of arrays with array destructuring
  • check the type of an object using the instanceOf operator
  • create a function from a string using the new keyword
  • create a new array by performing an operation on the elements on an existing one using the map() method
  • define and invoke a function which returns a nested function
  • generate deep and shallow copies of arrays and add and remove array elements
  • identify a number of object methods to access the keys and values of an object
  • implement an object constructor and use it to instantiate new objects
  • initialize an empty object and add/remove properties to/from that object
  • insert elements into the middle of arrays using splice and create slices of arrays using the slice method
  • perform aggregate and filter operations on the contents of an array using the reduce() and filter() methods
  • prevent changes from being made to an object by freezing it
  • recognize the role of the "this" keyword within the scope of a JavaScript object
  • recognize what data types in JavaScript are passed by value and by reference
  • use function callbacks to ensure the sequential execution of functions
  • use the call, apply, and bind methods to link a function invocation with an object
  • use the call method to link a JavaScript object to a function call
  • use the rest parameter syntax to create functions with an undefined number of parameters
  • use the spread operator to expand the contents of arrays
  • use the spread syntax and the JSON object to create new objects

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