JavaScript Functions Test

Check your knowledge of function declarations, parameters, closures, callbacks and arrow functions.

6 questions. Choose the best answer for each question, then review every explanation.

Question 1 of 6

1 of 6

Question 1Which function can normally be called before its declaration appears in the source?

A let function expressionAn imported default valueA function declarationA const arrow function

Question 2How does an arrow function determine this?

It inherits this from the surrounding scopeIt creates a new this for every callIt always uses windowIt always uses undefined

Question 3What value is returned?

function greet(name = 'Sam') {
    return `Hello ${name}`;
}

greet();

"Hello null"An error"Hello Sam""Hello undefined"

Question 4What does a rest parameter collect?

function total(...values) {}

Remaining arguments in an arrayAll arguments in an objectOnly the first argumentNamed parameters in a string

Question 5What is a closure?

A function that cannot accept argumentsA function retaining access to its lexical scopeA function with no return statementA method that closes the browser

Question 6What is a callback?

A function that can only run onceThe value returned by a loopA method defined on every objectA function passed for another function to invoke