Cleverse Academy tech test #1: Foundation JavaScript - Functions

js-functions-test.md

Cleverse Academy Tech Test #1: Foundation JavaScript

Functions

1. Parameters and return values

   1.1 Basic parameters and return values

   Given this function:

   function add(a, b) {
     return a + b;
   }

   1.1.1 How many parameters add accepts?

   1.1.2 What are the possible return types of add?

   1.1.3 What is the return value of add(1, 2)?

   1.1.4 What is the return value of add(1, "2")?

   1.1.5 What is the return value of add("foo", "bar", "baz")?

   1.1.6 What is the return value of add(1, 2, 3)?

   1.1.7 What is the return value of add(10, add(1, 2, 3))?

   1.2 Default parameters

   Given this function:

   function add(a, b = 10, c = 20) {
     return a + b + c;
   }

   1.2.1 How many arguments add accepts?

   1.2.2 What is the return value of add(1, 2)?

   1.2.3 What is the return value of add(1)?

   1.2.4 What is the return value of add(10, add(1, 2, 3))?

   1.3 Advanced function parameters

   function sum(...numbers) {
     // Body
   }

   sum is supposed to takes in variadic parameters (as indicated by the spread operator ...), and returns the sum of all numbers. For example, sum(10, 20, 30) should return 60.

   1.3.1 What is the variable type of numbers in sum's body?

   1.3.2 Implement sum with the above function signature.

2. Arrow functions

   2.1 Named functions

   Given this function:

   function isNeg(n) {
     return n < 0;
   }

   2.1.1 How many ways can we rewrite isNeg as an arrow function? (assuming we keep the expression n < 0 unchanged)

   2.1.2 What is the least verbose way (least characters used) to rewrite isNeg as an arrow function?

   Now, if we have this function:

   function assignLegalAge(obj) {
     obj.age = 18;
   }

   assignLegalAge takes in an object obj and writes property obj.age to 18.

   2.1.3 How many ways can we rewrite assignLegalAge as an arrow function? (assuming we keep the statement obj.age = 18; unchanged)

   2.1.4 What is the least verbose way (least characters used) to rewrite assignLegalAge as an arrow function?

   2.1.5 What is the difference between assignLegalAge and isNeg that made your 2.1.3 answer differ from 2.1.1?

   2.2 Anonymous (unnamed) functions

   2.2.1 Rewrite the following snippet with arrow function:

   const negs = nums.filter(function (n) {
     return n < 0;
   });

   2.3 Methods

   2.3.1 What is a method?

   2.3.2 Give 3 examples of methods on JavaScript string type

   2.3.3 Give 3 examples of methods on JavaScript Array type

   2.4 Iterator methods

   2.4.1 What is the return value of a callback function passed into Array.filter method?

   2.4.2 What is the return type of the Array.filter method?

   Now, given this snippet:

   const numbers = [-2, -1, 0, 1, 2];
   const isNegs = numbers.map(cb);
   const negs = numbers.filter(cb);

   2.4.3 We can see that the callback passed into number.map and number.filter is identical: a named function cb.

   Replace cb with anonymous function that would make variables isNegs become [true, true, false, false, false], and negs [-2, -1].

   2.5 Advanced iterator

   Given this snippet:

   const numbers = [10, 20, 30, 40, 50];
   const result = numbers.map(cb);

   2.5.1 Implement cb as an annonymous arrow function such that result is [1, 3, 5].