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How to work wisely with Array Iteration right from scratch?

Array iteration becomes a habitual practice to bring excellence to computers. An iteration on the other hand has been a constantly repeated process. It can also be compared to a kid watching the same cartoon over and over again. Who knew computer science follows that and does the same operations continually? Yes, it accomplishes.

Image credits - Medium

What is an array iteration?

Array iteration happens to be an iteration as well. Array iterations work in a serial method to get the job done. An iteration can be performed numerous times on each thing until the desired outcome flows. Not only does it get to the solution but also it increases 10x performance. We shall now see the variety of array iterations and their tasks.

forEach() in array iteration.

  • This one summons each item for each array once. It could also be called a callback function of the array iteration.

  • It indeed carries on three arguments such as the value, the index and the array.

Ex: const numbers = [1, 3, 5, 7,9]; let txt = " "; numbers.forEach(myFunction); function myFunction(value) 
txt += value + "<br>"; 
  • It shows the output of 1 3 5 7 9 in a vertical style unlike this in a row.

  • Here we have used just the value type alone because arguments have integers. You can use the index or array itself in place of 'value' when the situation arises.

Array map() in array iteration.

  • The map( ) helps in running a function for each array element. It also gives the brand new array once it has finished it.

  • However, it works with the aid of array values for array components.

  • It doesn't change the existing array too yet it delivers the fresh one out.

  • This too can do the job of the value, the index and the array.

  • We shall take the one where it multiplies the items by 3 for instance.

Hence, const numbers1 = [5, 3, 4, 2, 1];
const numbers2 =;
function myFunction(value) 
return value * 3 
It goes on with the outflow of 15, 9, 12, 6, 3.

filter() in array iteration

  • This method now filters the values, aspects of arrays or the array once it aligns with a set of rules.

  • We still utilise the filter( ) with the one to form a new array that can be above the value 10.

  • Likewise, it serves three arguments as value, index or array.

Ex: const numbers = [50, 5, 20, 6, 9]; 
const over10 = numbers. filter(myFunction); 
function myFunction(value) 
return value > 10; 
It results in the outcome as '50, 20' as both are greater than ten.


  • This 'reduce( )' technique lessens the array and its things into a total of the values.

  • For instance, imagine we have a group of numbers.

  • The reduce method will discover the sum of all the numbers and retrieve them as an output too.

  • It just allows the array entity to be a single value as deducted one.

  • It doesn't deduce the real array but rather permits the renewed array.

  • Despite that, it puts together four good things like total, index, value and array.

Ex: const digits = [25, 15, 20, 5,10]; 
let sum = digits.reduceRight(myFunction); 
function myFunction(total, value) 

return total + value;

Hence a total of all numbers ie., 75 will be the output.
  • ReduceRight( ) decreases the array of aspects from right to left into an individual value. Regardless, it carries out a similar total of the numbers inside the array.


  • The 'every( )' iteration inspects whether all the values in the array coordinate with the set of rules.

  • It should pass the trial as it must be above 10 and not below that. Hence the value items that pass the test successfully will enter into the outflow.

  • It gets checked out with three main arguments like value, index and array.

Ex: const numbers = [100,300,200,400]; 
let allOver200 = numbers.every(myFunction); 
function myFunction(value) 
return value > 200; 
  • It produces the output of all over 200 must be false due to some elements not being higher than 200.


  • This method examines whether some of the factors in an array pass the assignment given.

  • Let's take the examination as some number of integers of an array should be more than 75. The result doesn't go with the exam if you don't get an all-pass.

  • This also has three other aspects such as value, index and array.

Ex: const numbers = [50, 80, 70,100,200];
let someOver75 = numbers.some(myFunction); 
function myFunction(value) 

return value > 75; 

  • The output will be some over 75 must be true since some digits happen to be larger than 75.


  • The syntax of this method must be an array.indexOf(item, start). Here the item to look for is mandatory and the start states which value to initiate with is not necessarily added.

  • The index of the ( ) technique looks for the position value of a certain array facet and then recovers its role.

  • You need to note that the first factor occurs as zero, the second element as one and so on.

Ex: const names = ["Ram", "Sita", "Ram", "Lakshman"]; 
let position = names.indexOf("Ram") + 1; 
and the output will be Ram is in position 1.
  • It conveys the output of -1 when the element is not there.

  • It defines the first coming item value when the element has been more than once.

  • Whereas you can make use of the lastIndexof( ) method to find out the last position of the same element.


  • The find( ) procedure uncovers the first product once it filters out the desired function.

  • Likewise, we can use a sample of numbers larger than 200. It then supplies the first piece of the item that would be bigger than the digit 200.

  • It involves three arguments like value, index and array too.

Ex: const digits = [150,50,350,250,60]; 
let first = digits.find(myFunction); 
function myFunction(value) 
return value > 200; 

This results in an output of 350 because the first number over 200 is 350.


  • Unlike the before process, this find index( ) method locates the index of the specific value. The specific value should consist of the answer for the test conducted.

  • Similarly, we can utilize the number to be smaller than the 100 rule.

  • This one too has many types of values, indexes and arrays to work with.

Ex: const numerals = [200,150,300,400,90]; 
let first = numerals.findIndex(myFunction); 
function myFunction(value) 
return value < 100; 
  • This creates the output of the index value of 4 because the number lesser than 100 occurs in the fourth place.

Array. from()

  • This type of method functions in a way to enhance an object or an array into a string of values or variables.

  • This assigns the length of an array along with that.

Ex: Array.from("AEIOU"); puts the output as A, E, I, O, U.


This kind of key ( ) will hand out the keys of the array object and return them as an output.

Ex: const days = ["Sunday", "Monday", "Tuesday", "Wednesday"];

const keys = days.keys();

for (let x of keys) {

  text += x + "<br>";


It will give the output of the assigned keys 0, 1, 2, and 3 in a vertical column.

Array Destruction/Destructuring

Array destruction doesn't particularly mean demolition, instead it just means destructure. Yes, we can take the help of this strategy to unload values from an array to different variables. We can view a model of how to destructure an array.

Ex: let integers = [6, 7, 8, 9,10];
let [firstNumber] = integers;
console.log(firstNumber); output returns 6.

The numbers from 6 to 10 are issued to the variable integers. It in turn excerpts the first number and keeps it in the first number variable. After that, the program records the first number in the console that yields 6. We need to cover the powerful feature called the rest function. The rest operator segregation the rest of the items to make the new array.

It doesn't touch the original array also. This often can be helpful in varied situations like in arrays, objects or even in arguments. The destructure strategy again can be used along with this one. Especially if we need to separate the set of array elements after a cycle of destructuring arrays.


We have seen the arrays as a whole in Javascript right from a to z. I am sure it would have been much easier to interpret rather than those huge textbooks. One of them happens to be the training course that we provide for all. This training program contains the distinct type of classes and topics to be filled in.

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What is for loop?

The loop can come in handy when you work with the same thing again and again. The for loop makes a loop with once, many or a special condition. It runs as many times as it has coded upon. It offers the needed solution till the case becomes untrue.

What is a while loop?

The 'While loop' performs numerous times until the situation has been fulfilled. The block of regulation keeps ongoing as loops with repeated operations that could be not learned beforehand.

Can we use an iterator as a loop?

No, we can't use an iterator as a loop because it has been an object throughout JS. It can be aided by using a loop with a list of arrays or so. Though the remark for looping arises as an iterating and hence the word iterator.

Watch the brief visual here-


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