1. forEach

array.forEach() method is going to simply iterate all the elements in array.

Using with array.forEach()

let userData=['Raj','kumar','Thangavel'];
userData.foreach((data,index)=>{
   console.log(index); // Index of the array
   console.log(data) // Raj, Kumar, Thangavel
})

Without using array.forEach()

let userData=['Raj','kumar','Thangavel'];
for(let i=0;i<userData.length;i++){
   console.log(i); // Index of the array
   console.log(userData[i]) // Raj, Kumar, Thangavel
}

2. map

1. iterate all the elements in input array.
2. It's return a new array.

using using array.map()

const userData = ["raj","kumar"];
let newUserData = userData.map((user)=>user)
console.log(newUserData);  // raj, kumar

Without using array.map()

const userData = ["raj","kumar"];
let newUserData = [];
for(let i = 0; i < userData.length; i++){
    newUserData.push(arr[i])
}
console.log(newUserData);  // raj, kumar

3. filter

1. Iterate all the elements in input array and we need to write some condition and return it. Basically condition is return boolean (True/False).
2. If It is return true, each data will be return. If It is return false, data will not return.
3. It's return a new array.

with using array.filter()

const words = ['spray', 'limit', 'elite', 'exuberant', 'destruction', 'present'];

const result = words.filter(word => word.length > 6); // Conditions will return boolean only.

console.log(result);
// expected output: Array ["exuberant", "destruction", "present"]

without using array.filter()

const words = ['spray', 'limit', 'elite', 'exuberant', 'destruction', 'present'];
const result=[];
for(let i=0;i<words.length;i++){
    if(word.length > 6){
        result.push(words[i])
    }
}

console.log(result);
// expected output: Array ["exuberant", "destruction", "present"]

4.find

1. It helps to find the value in array (only the first value).
2. It is return value only.

with using arrary.find()

const array1 = [5, 12, 8, 130, 44];

const found = array1.find(element => element > 10);

console.log(found);
// expected output: 12

without using arrary.find()

const array1 = [5, 12, 8, 130, 44];

let found;

for(let i=0;i<array1.length;i++){
    if(element => element > 10){
       found=array1[i];
       break;
    }
}

console.log(found);
// expected output: 12

5. Reduce

1. It's going to take two Parameters. The first is the previousValue and the second is the currentValue.

2. previousValue is which we return the every elements along with arithmetic operation.

3. currentValue is each of the elements in arrary.

Let’s understand this method with an example:

const array1 = [1, 2, 3, 4];

let result=array1.reduce((previousValue, currentValue) => previousValue + currentValue);
// 1 + 2 + 3 + 4

console.log(result)
// expected output: 10

Without using Reduce method,

const array1 = [1, 2, 3, 4];
let result=0;
for(let i=0;i<array1.length;i++){
result=result+array1[i]
}
console.log(result); 
// expected output: 10

6. Some

1. It is return boolean. (True/False)
2. At least one elements will be matched with condition and it will return true or else It will return false.

with using Some method,

const inputArray = [1, 2, 3, 4, 5];

// checks whether an element is even
const even = (element) => element % 2 === 0;

console.log(inputArray.some(even));
// expected output: true

without using Some method

const inputArray = [1, 2, 3, 4, 5];
let result;
for(let i=0;i<inputArray.length;i++){
     if(inputArray[i]% 2 === 0){
         result=true;
         break;
     }else{
           result=false;
     }
}
console.log(result);
// expected output: true

7. Every

1. It is return boolean. (True/False)
2. Every Each of the elements will be matched with one condition and it will return true or else It will return false.

with using Every method,

const array1 = [1, 30, 39, 29, 10, 13];

const isBelowThreshold = (currentValue) => currentValue < 40;

console.log(array1.every(isBelowThreshold));
// expected output: true

without using Every method,

const array1 = [1, 30, 39, 29, 10, 13];
let result;
for(let i=0;i<array1.length;i++){
     if(array1[i]<40){
        result=true;
     }else{
        result=false;
       break;
    }
}

console.log(result);
// expected output: true

8. FindIndex

1. This method return Index value.
2. It will return index of the first element based on the input value condition. Otherwise It will return -1.

with using FindIndex method,

const array1 = [5, 12, 8, 130, 44];

const isLargeNumber = (element) => element > 13;

console.log(array1.findIndex(isLargeNumber));
// expected output: 3

without using FindIndex method,

const array1 = [5, 12, 8, 130, 44];
let indexValue;

const isLargeNumber = (element) => element > 13;

for(let i=0;i<array1.length;i++){
    if(array1[i] > 13){
      indexValue=i;
      break;
    }else{
      indexValue=-1;
    }
}
console.log(indexValue);
// expected output: 3

9. Keys

Keys method helps to return each index in the array.

with using Keys method,

const array1 = ['a', 'b', 'c'];
const iterator = array1.keys();

for (const key of iterator) {
  console.log(key);
}

// expected output: 0
// expected output: 1
// expected output: 2

without using Keys method,

const array1 = ['a', 'b', 'c'];
for(let i=0;i<array1.length;i++){
    console.log(i);
}
// expected output: 0
// expected output: 1
// expected output: 2

10. values

The values method returns each element in the array.

with using values method,

const array1 = ['a', 'b', 'c'];
const iterator = array1.keys();

for (const value of iterator) {
  console.log(key);
}

// expected output: a
// expected output: b
// expected output: c

without using values method,

const array1 = ['a', 'b', 'c'];
for(let i=0;i<array1.length;i++){
    console.log(array1[i]);
}
// expected output: a
// expected output: b
// expected output: c

Don't existing legacy code, Use Array helper Methods. It is simple and reduce your code .

My resent blog:

*Top ES6 Features - Every Javascript Developer Must know...! *🤔

thisisraj.hashnode.dev/top-es6-features-eve..