With arrays, there are usually a set number of specific things you want to achieve. Below is a list of pretty much any action you would want to perform on an array, and how to do it in Javascript. If you have any more, let me know in the comments below! 1. Find the Index of an Element by Value Use : indexOf let arr1 = [ 'potato', 'banana', 'ravioli', 'carrot' ]; // Returns 1 console.log(arr1.indexOf('banana')); // Returns -1 since not found console.log(arr1.indexOf('beetroot')); 2. Delete at Index Use : splice() let arr1 = [ 'potato', 'banana', 'ravioli', 'carrot' ]; // Returns [ 'banana', 'ravioli', 'carrot' ], since potato has index 0. arr1.splice(0, 1); console.log(arr1); 3. Delete at Index by Value Use and : splice() indexOf let arr1 = [ 'potato', 'banana', 'ravioli', 'carrot' ]; let itemIndex = arr1.indexOf('ravioli'); // Returns [ 'potato', 'banana', 'carrot' ], since ravioli has an index of 2 arr1.splice(itemIndex, 1); console.log(arr1); 4. Get the last element of an array Use : arr.length() - 1 let arr1 = [ 'potato', 'banana', 'ravioli', 'carrot' ]; // Returns carrot console.log(arr1[arr1.length - 1]); 5. Insert at Index Use . You can also read about inserting at an index in detail . splice() here let arr1 = [ 'potato', 'banana', 'ravioli', 'carrot' ]; // Inserts broccoli at position 2, after deleting 0 items arr1.splice(2, 0, 'broccoli'); // Returns [ 'potato', 'banana', 'ravioli', 'brccoli', 'carrot' ] console.log(arr1); 6. Remove the last element of the array Use : pop() let arr1 = [ 1, 2, 3, 4, 5, 6 ]; // Returns 6 console.log(arr1.pop()); // Returns [ 1, 2, 3, 4, 5 ] - last element is removed console.log(arr1); 7. Change all values of an array in the same way Use : map() let arr1 = [ 1, 2, 3, 4, 5, 6 ]; let newArr = arr1.map(function(arrElement) { return arrElement + 3; }) // ES6 version for modern browsers and NodeJS let anotherVersion = arr1.map( el => el + 3); // Returns [ 4, 5, 6, 7, 8, 9 ] for both console.log(newArr); console.log(anotherVersion); 8. Turn a string, map, or set into an array Use : Array.from() let newSet = new Set([ 'orange', 'apple', 'potato', 'spinach' ]); let newMap = new Map([ 'orange', 'apple', 'potato', 'spinach' ]); let newString = 'apple'; console.log(Array.from(newSet)); // Returns [ 'orange', 'apple', 'potato', 'spinach' ] console.log(Array.from(newMap)); // Returns [ 'orange', 'apple', 'potato', 'spinach' ] console.log(Array.from(newString)); // Returns [ 'a', 'p', 'p', 'l', 'e' ] 9. Check if it is an array Use : Array.isArray() let arr1 = [ 'orange', 'apple', 'potato', 'spinach' ]; let obj1 = { myKey: "myValue" } console.log(Array.isArray(arr1)); // Returns true console.log(Array.isArray(obj1)); // Returns false 10. Check every element in an Array Use : forEach let arr1 = [ 'orange', 'apple', 'potato', 'spinach' ]; arr1.forEach(function(item) { console.log(item); // Returns each array item individually }); 11. Merge two arrays Use or : ... concat let arr1 = [ 'orange', 'apple' ]; let arr2 = [ 'potato', 'spinach' ]; // For legacy browsers (ES5); // Returns [ 'orange', 'apple', 'potato', 'spinach' ]; let someArray = arr1.concat(object); // For modern Javascript (ES6/NodeJS) // Returns [ 'orange', 'apple', 'potato', 'spinach' ]; let someOtherArray = [ ...arr1, ...arr2 ]; 12. Turn object names into an array Use : Object.keys let object = { name1: "value", name2: "value", name3: "value" }; // Returns [ 'name1', 'name2', 'name3' ]; let array = Object.keys(object); 13. Turn object values into arrays Use : Object.values let object = { name1: "value", name2: "value", name3: "value" }; // Returns [ 'value', 'value', 'value' ]; let array = Object.values(object); 14. Reverse an Array Use : reverse() let arr1 = [ 'potato', 'banana', 'carrot' ]; arr1.reverse(); // Returns [ 'carrot', 'banana', 'potato' ] console.log(arr1); 15. Sum all Elements in an Array Use : reduce() let arr1 = [ 1, 2, 3, 4, 5 ]; // For legacy browsers let getTotal = arr1.reduce(function (accumulator, currentNumber) { return accumulator + currentNumber }); // ES6 for modern browsers and NodeJS let theTotal = arr1.reduce((accumulator, currentNumber) => accumulator + currentNumber); // Returns 15 console.log(getTotal); 16. Add an Element to the end of an array Use : push() let arr1 = [ 'banana', 'potato' ]; arr1.push('broccoli'); // Returns [ 'banana', 'potato', 'broccoli' ] console.log(arr1); 17. Check if every element of an array passes a test Use every() let arr1 = [ 1, 2, 3, 4, 5, 6, 7 ]; // Will return true and console log 'great' if(arr1.every(value => value < 10)) { console.log('great!') } Also published . here
