Array.isArray(arr)

Array.isArray([1, 'something', true]);  // trueArray.isArray({anything: 123}); // falseArray.isArray('some string');   // falseArray.isArray(undefined);  // false

arr.length;

[].length;// 0[1, 'something', true].length;// 3

arr.forEach(callbackFn);const callbackFn = (arrItem, index) => {callbackFn Scope Code Exec}// combining above statements together into one line of codearr.forEach((arrItem, index) => {callbackFn Scope Code Exec});

['apple', 'banana', 'carrot'].forEach((arrItem, index) => {  console.log(index + ' => ' + arrItem);});// 0 => apple// 1 => banana// 2 => carrot

arr.map((arrItem, index) => { return resultIteration });

const arr = [2, 4, 6, 8, 16];const mapResult = arr.map(arrItem => arrItem * 2);console.log(mapResult);// [4, 8, 12, 16, 32]

arr.filter((arrItem, index) => { condition to return arrItem });

const arr = [2, 4, 6, 8, 16];const filterResult =   arr.filter(arrItem => arrItem < 5 || arrItem > 10);console.log(mapResult);// [2, 4, 16]

const arr = ['banana', 'orange', 'apple', 'mango'];arr.sort();// ['apple', 'banana', 'mango', 'orange']

const arr = [22, 14, 0, 100, 89, 201];arr.sort();// [0, 100, 14, 201, 22, 89]

// compareFn for ascending orderconst compareFnAsc = (a, b) => a - b;// compareFn for descending orderconst compareFnDes = (a, b) => b - a;const arr = [22, 14, 0, 100, 89, 201];arr.sort(compareFnAsc);// [0, 14, 22, 89, 100, 201]arr.sort(compareFnDes);// [201, 100, 89, 22, 14, 0]

arr.concat(value);arr.concat(value0, value1, ... , valueN);

// Example 1 // Concat 2 arrays of string and number typeconst letters = ['a', 'b', 'c'];const numbers = [1, 2, 3];
letters.concat(numbers);// ['a', 'b', 'c', 1, 2, 3]// Example 2 // Concat a string array with 2 values (number and number array)const letters = ['a', 'b', 'c'];
const alphaNumeric = letters.concat(1, [2, 3]);
console.log(alphaNumeric);// ['a', 'b', 'c', 1, 2, 3]

arr.every(callbackFn);const callbackFn = (arrItem, index) => {  condition to check on every arrItem}

const arr1 = [89, 0, -4, 34, -1, 10];const arr2 = [89, 0, 45, 34, 1, 100];arr1.every(arrItem => arrItem >= 0);// falsearr2.every(arrItem => arrItem >= 0);// true

const arr1 = [89, 0, 44, 34, -1, 10];const arr2 = [-8, -45, -1, -100, -9];arr1.some(arrItem => arrItem >= 0);// truearr2.some(arrItem => arrItem >= 0);// false

const arr = [1, "2", 3, 4, 5];// Type of matching argument should match with the array entry// In the code below 2 is of type number but in arr "2" is stringconsole.log(arr.includes(2));// falseconsole.log(arr.includes("2"));// true

arr.join();arr.join(separator);

const arr = ['Hello', 'World', '!'];arr.join();      // 'Hello,World,!'arr.join(', ');  // 'Hello, World, !'arr.join(' + '); // 'Hello + World + !'arr.join('');    // 'HelloWorld!'arr.join(' ');    // 'Hello World !'

const callbackFn = (total, currArrItem, index, arr) => { ... }arr.reduce(callbackFn, initVal)// Combining above statements into one statementarr.reduce((total, currArrItem, index, arr) => { ... }, initVal)

const arr = [1, 2, 3, 4];const reducer = (prevVal, currVal) => prevVal + currVal;arr.reduce(reducer);// 10// In the code below initVal is set to 5, which means that we have // to init the sum with initial value 5: 5 + 1 + 2 + 3 + 4 arr.reduce(reducer, 5);// 15

arr.find((arrItem) => condition to check on arrItem);

const arr = [5, 10, 100, 12, 8, 130, 44];const result = arr.find(arrItem => arrItem > 10);console.log(result);// 100

const arr = [5, 10, 100, 12, 8, 130, 44];const result1 = arr.findIndex(arrItem => arrItem > 10);const result2 = arr.findIndex(arrItem => arrItem > 1000);console.log(result1);// 2console.log(result2);// -1

const arr = [5, 10, 100, 12, 8, 130, 44];arr.indexOf(12);// 3// As the input argument '12' is of type string and the input array // arr elements are of type number so there will be no match in // input arrarr.indexOf('12');// -1

arr.fill(value)// default startIndex = 0arr.fill(value, startIndex)// default endIndex is arr.lengtharr.fill(value, startIndex, endIndex)

const arr1 = ['A', 'B', 'C', 'D', 'E', 'F', 'G', 'H'];arr1.fill(0);// [0, 0, 0, 0, 0, 0, 0, 0]const arr2 = ['A', 'B', 'C', 'D', 'E', 'F', 'G', 'H'];arr2.fill(0, 5);// ['A', 'B', 'C', 'D', 'E', 0, 0, 0]const arr3 = ['A', 'B', 'C', 'D', 'E', 'F', 'G', 'H'];arr3.fill(0, 5, 7);// ['A', 'B', 'C', 'D', 'E', 0, 0, 'H']const arr4 = [1, 2, 3, 4, 5];arr4.fill();//[undefined, undefined, undefined, undefined, undefined]

arr.slice()arr.slice(startIndex)arr.slice(startIndex, endIndex)

const arr = ['rats', 'sheep', 'cows', 'chickens', 'dogs', 1001];arr.slice();// ['rats', 'sheep', 'cows', 'chickens', 'dogs', 1001]arr.slice(3);// ['chickens', 'dogs', 1001]arr.slice(2, 5);// ['cows', 'chickens', 'dogs']arr.slice(-4);// ['cows', 'chickens', 'dogs', 1001]

arr.splice(startIndex)arr.splice(startIndex, deleteCount)arr.splice(startIndex, deleteCount, item1)arr.splice(startIndex, deleteCount, item1, ..., itemN)

// Example 1// Remove 0 items before index 2 & insert "drum"let arr = ['angel', 'clown', 'mandarin', 'sturgeon'];let removedArr = arr.splice(2, 0, 'drum');// arr: ["angel", "clown", "drum", "mandarin", "sturgeon"]// removedArr: []
// Example 2// Remove 0 items before index 2 & insert "drum", "guitar"let arr = ['angel', 'clown', 'mandarin', 'sturgeon'];let removedArr = arr.splice(2, 0, 'drum', 'guitar');// arr: ["angel", "clown", "drum", "guitar", "mandarin", "sturgeon"]// removedArr: []
// Example 3// Remove 1 element at index 3let arr = ['angel', 'clown', 'drum', 'mandarin', 'sturgeon'];let removedArr = myFish.splice(3, 1);// arr: ["angel", "clown", "drum", "sturgeon"]// removedArr: ["mandarin"]
// Example 4// Remove 1 element at index 2 & insert "trumpet"let arr = ['angel', 'clown', 'drum', 'sturgeon'];let removedArr = arr.splice(2, 1, 'trumpet');// arr: ["angel", "clown", "trumpet", "sturgeon"]// removedArr: ["drum"]
// Example 5// Remove 2 items from index 0 & insert "parrot", "anemone", "blue"let arr = ['angel', 'clown', 'trumpet', 'sturgeon'];let removedArr = arr.splice(0, 2, 'parrot', 'anemone', 'blue');// arr: ["parrot", "anemone", "blue", "trumpet", "sturgeon"]// removedArr: ["angel", "clown"]

const arr1 = [1, 2, 3];arr1.reverse();// [3, 2, 1]const arr2 = ['1', '4', '3', 1, 'some string', 100];arr2.reverse();// [100, 'some string', 1, '3', '4', '1']

arr.push(value);arr.push(value0, value1, ... , valueN);

const animals = ['cats', 'rats', 'sheep'];animals.push('cows');// 4console.log(animals);// ['cats', 'rats', 'sheep', 'cows']animals.push('chickens', 'dogs', 1001);// 7console.log(animals);// ['cats', 'rats', 'sheep', 'cows', 'chickens', 'dogs', 1001]

const arr = ['rats', 'sheep', 'cows', 'chickens', 'dogs', 1001];arr.pop();// 1001console.log(arr);// ['rats', 'sheep', 'cows', 'chickens', 'dogs']

const arr = ['rats', 'sheep', 'cows', 'chickens', 'dogs', 1001];arr.shift();// 'rats'console.log(arr);// ['sheep', 'cows', 'chickens', 'dogs', 1001]

const animals = ['cats', 'rats', 'sheep'];animals.unshift('cows');// 4console.log(animals);// ['cows', 'cats', 'rats', 'sheep']animals.unshift('chickens', 'dogs', 1001);// 7console.log(animals);// ['chickens', 'dogs', 1001, 'cows', 'cats', 'rats', 'sheep']

Array.of(1);         // [1]Array.of(1, 2, 3);   // [1, 2, 3]Array.of(undefined); // [undefined]

Array.from(value, callbackFn)

Array.from('hello');// ['h', 'e', 'l', 'l', 'o']Array.from([1, 2, 3], arrItem => arrItem * 4);// [4, 8, 12]

arr.flat()arr.flat(depth)

// Example 1const arr1 = [0, 1, 2, [3, 4]];console.log(arr1.flat());// [0, 1, 2, 3, 4]// Example 2const arr2 = [0, 1, 2, [[[3, 4]]]];console.log(arr2.flat(2));// [0, 1, 2, [3, 4]]console.log(arr2.flat(3));// [0, 1, 2, 3, 4]

arr.at(index)

const arr = ['chickens', 'dogs', 1001, 'cows', 'cats', 'sheep']arr.at(1);// 'dogs'arr.at(-1);// 'sheep'arr.at(2);// 1001arr.at(-2);// 'cats'arr.at(-100);// undefined