Exercises JavaScript

Exercise 1

Given an array of objects, get the object with id 3:

const arrNames = [ {id: 1, name: 'Pepe'}, {id: 2, name: 'Juan'}, {id: 3, name: 'Alba'}, {id: 4, name: 'Toby'}, {id: 5, name: 'Lala'} ]

Exercise 2

Given an array of values, return a truthy array (no null, empty, non-numbered, undefined or dummy values)

const arrDirty = [NaN, 0, 5, false, -1, '',undefined, 3, null, 'test']

Exercise 3

Given an array of cities, get all the cities in Spain that are not capitals.

const arrCities = [ {city: 'Logroño', country: 'Spain', capital: false}, {city: 'Paris', country: 'France', capital: true}, {city: 'Madrid', country: 'Spain', capital: true}, {city: 'Rome', country: 'Italy', capital: true}, {city: 'Oslo', country: 'Norway', capital: true}, {city: 'Jaén', country: 'Spain', capital: false} ]

Exercise 4

Given three arrays of numbers, draw into a new array the intersection of these arrays.

const arrNumber1 = [1,2,3]; const arrNumber2 = [1,2,3,4,5]; const arrNumber3 = [1,4,7,2];

Exercise 5

Given an array of cities, get in a new array the non-capital cities with new parameters that are city and isSpain. The value of isSpain will be a boolean indicating if it is a city in Spain.

const arrCities2 = [ {city: 'Logroño', country: 'Spain', capital: false}, {city: 'Bordeaux', country: 'France', capital: false}, {city: 'Madrid', country: 'Spain', capital: true}, {city: 'Florence', country: 'Italy', capital: true}, {city: 'Oslo', country: 'Norway', capital: true}, {city: 'Jaén', country: 'Spain', capital: false} ]

Exercise 6

Create a function that rounds a float number to a specified number of decimal places.

The function must have two parameters:

• First parameter is a float number with x decimal places.
• Second parameter is an int indicating the number of decimal places to round to.
• Avoid using the toFixed() method.

Example:

const roundedResult = roundTo(2.123, 2); console.log(roundedResult); // 2.12

const roundedResult = roundTo(1.123456789, 6); console.log(roundedResult); // 1.123457

Exercise 7

Create a function that returns the fields of an object that equal a "falsy" value after being executed by a specific function. The foundation must have two parameters:

• First parameter is an object with x number of fields and values.
• Second parameter is a function that returns a boolean, which has to be applied to the object of the first parameter.

Example:

const result = returnFalsyValues({ a: 1, b: '2', c: 3 }, x => typeof x === 'string')

console.log(result); // {a: 1, c: 3}

Exercise 8

Create a function that converts a number of bytes into a format with readable values ('B', 'KB', 'MB', 'GB', 'TB', 'PB', 'EB', 'ZB', 'YB'). The function must have 2 parameters:

• First parameter must be the number of bytes.
• Second parameter must be a number specifying the number of digits to truncate the result to (this can be done with Number.prototype.toPrecision()). By default, this parameter should have a value of 3.

Example:

const result = fromBytesToFormattedSizeUnits(1000); console.log(result); // 1KB

const result = fromBytesToFormattedSizeUnits(123456789); console.log(result); // 123MB

const result = fromBytesToFormattedSizeUnits(-12145489451.5932, 5); console.log(result); // -12.145GB

Exercise 9

Create a function that from an input object, returns an object making sure that the keys of the object are in lowercase. The function must have an object as its only parameter.

const myObject = { NamE: 'Charles', ADDress: 'Home Street' };

Exercise 10

Create a function that removes html or xml tags from a string. The function must have a string as its only parameter.

Example:

const result = removeHTMLTags('<div><span>lorem</span> <strong>ipsum</strong></div>');

console.log(result); // lorem ipsum

Exercise 11

Create a function that takes an array as a parameter and splits it into new arrays with as many elements as specified. The function must have two parameters:

• The first parameter is the integer array to be split.
• The second parameter is the number of elements that the arrays into which the original array of the first parameter is to be divided must have.

Example:

const result = splitArrayIntoChunks([1, 2, 3, 4, 5, 6, 7], 3); console.log(result); // [ [ 1, 2, 3 ], [ 4, 5, 6 ], [ 7 ] ]