Higher Order Function

forEach — Used for iteration

map — Used for Transform

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filter — Used for filter

• forEach is the higher Order function used for iteration on array only.
• forEach kuch return ni karta

var arr = [10, 'hey', 30, false]
let run = () => {
    console.log("Hello")
}
arr.forEach(run)

// Output : Hello Hello Hello Hello

var arr = ['ajay', 'bittu', 'chotu', 'dabbu']
arr.forEach(function(val) {
   console.log(val)
})

// output : ajay bittu chotu dabbu

var arr = ['ajay', 'bittu', 'chotu', 'dabbu']
arr.forEach(function(element, index) {
   console.log(index)
})

// Output : 0 1 2 3

var arr = ['ajay', 'bittu', 'chotu', 'dabbu']
arr.forEach(function(index, element) {
   console.log(index)
})

// output : ajay bittu chotu dabbu

// yahan hme elements milengey not index, because first is always element
// weather name should be anything and second prop is index always.

// Sum of Array Element

var arr = [10,20,30,40]
var sum = 0
arr.forEach(function(elem) {
   sum = sum + elem
})

console.log(sum)

// Output : 100

// Transform the array and find the square of each element

var arr = [10,20,30,40]
var arr2 = arr.map(function(elem){
   return elem * elem
})

console.log(arr2);

// filter

var arr = [5,9,2,4,33,8]
var arr2 = arr.filter(function(elem) {
    return elem > 0
})

console.log(arr2)

var arr = ["Aman", "Basundi", "chintu", "dev"]
// Iteration - forEach
var out = arr.forEach(function(elem){
   console.log(out)
})


// Trasformation

var out1 = arr.map(function() {
   return elem + 'Welcome'
})

var arr = ['aman', 'ajay', 'anju', 'rohit', 'kiran', 'akash']

arr.filter(function(elem){
   return elem.startsWith('a')
})