JavaScript iterations method

JavaScript 3 statement for looping:
1.For...of loop :
used to get the values of an array one by one.
For array we prefer for...of to get value.

let nums = [10, 20, 30];
for(let x of nums){
console.log(x);
}
output:
10
20
30

2.for...in loop :
used to access the keys or indexes of an array.
(Not recommended)

let nums = [10, 20, 30];
for(let i in nums){
console.log(i);
}

3.forEach() :
Execute/ calls a function for each array element. it doesn't create a new array.

const numbers = [45, 4, 9, 16, 25];
numbers.forEach(myFunction);

//function myFunction(value, index, array)
function myFunction(value){
  console.log(value);
}
output :
45
4
9
16
25

notes : within function we can give 3 arguments(value index, array).

4.map() :
create a new array transforming/performing a function each element.

const num1=[1, 2, 3];
const num2= num1.map(myFunction);

//function myFunction(value, index, array)
function myFunction(value){
return value*2;
}
console.log(num2);

5.flatMap() :
first map each array element then create new array by flatten the array.

let nums = [1, 2, 3];
let result = nums.flatMap(n => [n, n * 10]);
console.log(result); //1,10,2,20,3,30

6.filter() :
create new array containing only elements that satisfy a condition.

let nums = [10, 15,20,25];
let result = nums.filter(myFunction);
function myFunction(value){
return value >15;
}
or
let nums = [10, 15,20,25];
let result = nums.filter(n => n > 15);
console.log(result);   //[20, 25]

7.reduce()
combines array elements into single result.
note : works from left to right.

let nums = [10,20,30];
let result = nums.reduce((total, n) => total + n, 0);
console.log(result);   //60

8.reduceRight() :
works from right to left

9.every() :
checks all elements satisfy a condition.
returns true or false.

let nums = [10,20,30];

console.log(nums.every(n => n>5));  //true
console.log(nums.every(n => n>15));//false

10.some() :
checks at least one element satisfies a condition.

let nums = [10,20,30];

console.log(nums.every(n => n>5));  //true
console.log(nums.every(n => n>15));//true

11.Array.from() :
create a new array from a iterable or array like value , string.

let text = "CAT";
let result = Array.from(text);
console.log(result);

output: ["C", "A", "T"]

12.keys() :
returns an iterator containing the array's indexes.

let fruits = ["apple", "mango", "orange"];
console.log([...fruits.keys()]);

output : [0, 1, 2]

13.spread operator(...) :
spread expands an array's elements. it is used to copy or combine arrays.

let a = [10,20, 30];
let b = [...a];
console.log(b);   //[10, 20, 30]

let a = [10, 20];
let b = [30, 40];
console.log(...a, ...b);   //[10, 20, 30, 40]

14.rest parameter(...) :
rest collects arguments into single array. spread and rest are same but differ purpose.

function add(...nums){
return nums.reduce((total, n) => total + n, 0);
}
console.log(add(10, 20, 30));   //60