Javascript Foreach: Working with Arrays

Jascript foreach is a powerful tool for working with arrays. It makes it easy to iterate through the items in an array and perform operations on each item. If you are not sure what javascript foreach is, then this article will tell you all about how javascript foreach works, as well as some of its most common uses.

How JavaScript foreach works

The javascript foreach keyword iterates through an array and executes the following statements for each item in turn. If you haven’t used javascript before, then it’s worth reading this article to get started with javascript:

Syntax:

myArray.forEach(element => console.log(element));

Example:

let myArray = ['abc', 'bcd', 'efg']

 myArray.forEach(element => console.log(element));

//This javascript foreach process will execute the following statements: 

console.log('abc') // Executes for first item in array, which is 'abc'.

 console.log('bcd') // Executes for second item in array, which is 'bcd'. console.log('efg') //Executed third time

Parameters:

  • Current Value (required) – The current value of Array
  • Index (optional) – Index number of current element
  • Array (optional) – This belongs to current Array element

Parameters Description:

Current Value (required): With the use of a forEach method, you can loop through an array with ease. This is done by creating an anonymous (or callback) function and executing it within your desired code statement.

Examaple:

myArray.forEach(function(ary) {
    conosle.log(ary)
});

At the time of execution of the above function it execute every single element of array. It take atleast one parameter which hold the array’s value.

Index(optional): The index parameters is optional parameters which is optional. The index parameter only show the index number of current array element.

Example:

myArray.forEach((ary, indexNo) => {
    console.log('Index: ' + indexNo+ ' Value: ' + ary);
});

The above code has two parametes that return two value first one is the index number of current array. Another is return the array’s value one by one.

Array (optional): The Array parameter is optional just because it only print the array many time I mean it will print the array as the number or array element.

myArray.forEach((ary, index, array ) => {
    console.log(array);
});

Description:

forEach() is a JavaScript function that allows you to iterate through an array. It operates by checking each element in the array and calling your provided callbackFn for every one of them, starting with index 0 and ending at (but not including) the length-1 value. Any elements which are deleted or uninitialized will be skipped entirely–you’ll never get into trouble if those values don’t exist!

The callback function is called with three arguments: the following objects are passed as parameters:

  • The current element in the array.
  • The index of the current element in the array (starting at 0).
  • A reference to this object, so that you can continue chaining functions for each iteration.

When a callback function is passed to forEach(), this value of that callback can be set by specifying it as an argument. The actual this seen by any given callback will depend on how arguments are coerced, but ordinarily, they would default to undefined if no explicit conversion takes place.

The forEach() method is a handy utility function, which visits each element in an array. It iterates through the elements of the given array and executes callbackFn(value) with each one it finds; if that value has already been seen by this iteration of forEach(), then nothing happens – but when values are changed during the course of iterations on any other part or elsewhere, those changes will be reflected immediately inside callbackFn().

NOTE: There is no way to stop or break a forEach() loop other than by throwing an exception. If you need such behavior, the method may not be appropriate for your needs and should be avoided in this situation.

The early termination accomplished by :

  • A simple for loop
  • A for…of / for…in loops
  • Array.prototype.every()
  • Array.prototype.some()
  • Array.prototype.find()
  • Array.prototype.findIndex()

NOTE: One of the best aspects of forEach is that it does not need to wait around for promises. This allows you to quickly run through all your data and get back on with life without having to worry about a potentially infinite chain reaction from one single promise failing because someone clicked ‘close’ before they could finish inputting text into an unending form field, etcetera.

Example:

let myArray = [5, 4, 5];
let mySum = 0;

let mySumFunction = async function (a, b)
{
  return a + b
}

myArray .forEach(async function(elem) {
  mySum = await sumFunction(sum, rating)
})

console.log(mySum )

How foreach is different

Javascript for loop is a bit more simple and does not allow you to iterate over arrays, unlike the foreach loop. Foreach loops are capable of iterating through an array while also being able to work with other objects like dictionaries or even just plain strings if needed.

Conclusion:

With this blog post, I hope you have gained a greater understanding of how to use the foreach loop in javascript. We’ve covered all the basics and some more advanced topics as well. If there is something that you still need help with or would like to learn about, feel free to contact us at any time. You can also check out our website for further learning materials on JavaScript arrays! AdvDev.net

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