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arrays_examples.js
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arrays_examples.js
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/**
Array examples
*/
/* Basic methods */
// 1. Join an array with -
const joinString = [1, 2, 3, 4].join('-');
// 2. Reverse an array
[1, 2, 3, 4].reverse();
// 3. Sort an array
[4, 2, 3, 1].sort();
// 4. Sort an array with a reverse sort function
[1, 4, 2, 3].sort((a, b) => a < b);
// 5. Use concat with empty array and three params
[].concat([1, 2], [3, 4], [5, 6]);
// 6. Use concat with array and then comma-separated params
[].concat(1, 2, [3, 4, 5, 6]);
/* More advanced methods */
// 1. Map a square function
[1, 2, 3, 4].map(e => e * e);
// 2. Map a function which takes an array of lowercase brands and makes all uppercase
['nike', 'adidas', 'puma'].map(m => m.toUpperCase());
// 3. Filter a function for valid SSN with the correct length
['1111902319', '1011892319', 'NONVALIDSSN'].filter(m => /[0-9]{10}/g.test(m));
// 4. Filter all odd numbers which are larger than 5
[1, 2, 3, 4, 5, 6, 7, 8, 9, 10].filter(e => e % 2 !== 0 && e > 5);
// 5. Evaluate if every element are a typeof function (should pass)
[() => {}, () => {}].every(e => typeof e === 'function');
// 6. Evaluate if every element is larger than 10
[1, 2, 3, 4, 20].every(e => e > 10);
// 7. Evaluate if some elements are squared equal to 4
[1, 2, 3, 4].some(e => e * e === 4);
// 8. Reduce all elements and calculate the average
const averageArray = [1, 2, 3, 4];
const average = averageArray.reduce((total, elem) => total + elem) / averageArray.length;
// 9. Reduce a reversed string
['o', 'l', 'l', 'e', 'H'].reduceRight((total, elem) => total + elem);
// 10. Use indexOf to find a specific element within an array
// 10.1. integer
[1, 2, 3, 4].indexOf(3);
// 10.2. object
const elem = { a: 1, b: 2};
const array = [elem];
array.lastIndexOf(elem);