Array Methods : : 1. ITERATION METHODS : Observe the context of an Array. Examination Methods : Derive a new array from receiver. Transformation Methods : Compute a result based on the receiver's element. Reduction Methods : Iterating Arrays from Loops. From Loops 1.1 Examination Methods 1.1.1 Array.forEach(callback, thisValue?) Iterates over the every entry of an array. It takes a callback function where you can code. You cannot break out of it or return a value from it. Example : 1.1.2 Array.every(callback, thisValue?) Returns true, if the callback returns true for every element. It will stop iteration as soon as the callback return false. Example : 1.1.3 Array.some(callback, thisValue?) Returns true, if the callback returns true for at least one element. It stops iteration as soon as the callback returns true. Example : 1.2. Transformation Methods 1.2.1 Array.map(callback, thisValue?) : Copy while giving new values to elements. This will map all the values to an expression & returns a modified copy of the array leaving original untouched. Example : 1.2.2 Array.filter(callback, thisValue?) : Only keep some of the elements. This will only keep the elements which will match the condition & returns modified copy of the array leaving original untouched. Example : 1.3. Reduction Methods 1.3.1 Array.reduce(callback, initialValue?) : deriving a value from an Array This will reduce all the elements to a single value & reducer takes value and accumulator. Accumulator is required to be set to a starting value & returns modified copy of the array leaving original untouched. function total Example : 1.4. Iterating Arrays from Loops 1.4.1 For Loops The is one of the basic loops for looping through an array. It takes a starting index and then loops through to the ending index. Index === Integer. for loop Example : 1.4.2 While Loops The will loop whenever a condition stays true. This code below uses a while loop. In each loop iteration, it removes the first element of array via .shift() and logs it. while loop Example : 1.4.3 Do-while Loops The loop works much like , but it will check its condition after each loop iteration(not before) & it will always execute first iteration. do-while while loops Example : : 2. ARRAY CONSTRUCTOR METHODS 2.1 Array.isArray(object) Returns true if object is an array. It is a convenient way to check if the element is an array. Example : 3. ARRAY PROTOTYPE METHODS : These are grouped by functionality : : They change the arrays that they are invoked on. Destructive : They don't modify their receivers, such methods often return new arrays Non-Destructive 3.1. Destructive Methods 3.1.1 Array.shift() Removes the element at index 0 and returns it. The indices of subsequent elements are decremented by 1. Example : 3.1.2 Array.unshift(elem1?, elem2?, ...) Prepends the given elements to the array. It returns the new length. Example : 3.1.3 Array.pop() Removes the last element of the array and returns it. Example : 3.1.4 Array.push(elem1?, elem2?, ...) Adds the given elements to the end of the array. It returns the new length. Example : 3.1.5 Array.splice(startIndex, delete Count?, elem1?, elem2?, ...) Starting at , removes elements and insert the given elements. In simple words, we are replacing the deleteCount elements at position with , and so on. This method returns the elements that have been removed. Start can be negative = (-1) refers the last element, and so on. startIndex delete-Count startIndex elem1, elem2 Example : 3.1.6 Array.reverse() Reverse the order of the elements in the array and returns a reference to the original(modified) array. Example : 3.1.7 Array.fill(new-element, start-index, end-Index) will add or replace the element with the element specified from to . If is not defined then it will start from 0, if is not defined, then it will change values up to end of the array. Array.fill start Index end Index start Index end index Example : 3.1.8 Array.sort(compare-function?) It will sort the array and returns it. This sorting compares values by converting them to strings, which means that numbers are not sorted numerically we can fix this by providing the optional parameter . compareFunction() Example : 3.2 Non-Destructive Methods 3.2.1 Array.concat(arr1?, arr2?, ... ) Creates a new array that contains all the elements of the receiver, if one of the parameters is not an array, then it is added to the result as an element. so if we can say in simple words, it will add different array elements to the new array. Example : 3.2.2 Array.join(separator?) This will return a string by concatenating the entries after they are converted to string with the separator between each entry. Works best with the string and number arrays. If separator is omitted, is used. ',' Example : 3.2.3 Array.slice(startIndex?, endIndex?) It will copy array elements into a new array, starting at , until and excluding the element at ,which means to . If either of the indices is negative then the array length is added to it, thus, (-1) refers to the last element, and so on. start Index end Index start Index endIndex-1 Example : 3.2.4 Array.includes() checks if an item exits in an array. It takes a number or string which the function can compare. Array.includes() Example : 3.2.5 Array.indexOf(searchaValue, startIndex?) It will search the array for , starting at . It returns the index of the first occurrence or if nothing is found it returns . if is negative, the array length is added to it & if it is missing, the whole array is searched. search Value start Index -1 start Index Example : 3.2.6 Array.lastIndexOf(searchElement, startIndex?) It will search the array for , starting at , backward. It returns the index of the first occurrence or if nothing found it returns . search Element start Index -1 Example : 4. SOME OTHER IMPORTANT ARRAY METHODS : 4.1 Remove Duplicates in Array 4.1.1 Array.from(new Set(array)) is an object that cannot have duplicates entries. You can create a new from an array then convert it back to an array. Set Set Example : 4.2 Find Element in Array 4.2.1 Array.find() will return the element in the array with the given condition. Example, if we want to get certain elements from array & work on that element separately. Array.find Example : 4.2.2 Array.findIndex() will return the index of the element in the array with the given condition. it is same as method but only difference is only works with primitive values. if you wish to find an in the array, you need to use method . Array.findIndex indexOf indexOf object(array, object or function) findIndex Example : Manipulation of Arrays with just Array.slice() and Array.concat(). There are so many methods like , , , , and because they're easier to use as a beginner, if we open any book or website, they have used these methods to manipulate the arrays. But these methods mutate arrays to ensure arrays don't mutate. you can use and over these five methods As these two are non-destructive methods which doesn't modify the existing array and they will return a new array. push pop shift unshift splice slice concat 1. Adding Elements 1.1 Adding items to the beginning of array. Convert items to add into an array(if they're not one already) Combine the arrays together with concat Example : 1.2 Adding items to the end of array We can add elements to the end of an array with a method called . concat Example : 1.3 Adding items to the middle of an array The idea is to add elements to the middle of an array is to split your array into two parts with then join three arrays together in this sequence : . slice first part, items to add, second part Example : 2. Removing Elements 2.1 Removing items from the front We can remove elements from the front of an array with a method . slice Example : 2.2 Removing items from the end We can use same method to remove elements from the front of an array. but first we will need to pass correct value. So that you can remove the last item and can use as your value. endIndex Array.length - 1 endIndex Example : 2.3 Removing items from the middle Removing items from the middle of an array is trickier then to removing item from the end. The idea is to copy the parts you want to retain with then join the copied arrays together with . slice concat Example : Follow me on Instagram @hypnosisss___ &Twitter @akash_Rajvanshi Check out my other productivity tools posts: Complete Setup For Home Media Server!! Setting Up Manjaro Linux From Scratch!! Setting Up Visual Studio Code For Front_End_Development!!
