Different iteration statements in javascript

1) for loop for loop will repeat until a specified condition met.

for([initialExpression],[conditionExpression],[incrementExpression])

example

const arr = [10,20,25,55,60,80,95];
let count = 0;
for(let i=0; i < arr.length; i++){
     if(arr[i] % 10 === 0){
            count++;
     }
}
console.log(count) // 4

here for loop runs until the i value becomes more than the length of an array.

2) for...in

for-in is used to iterate over the properties of object
for-in loop iterates only over those keys of an object which have their enumerable property set to “true”
order of execution and properties defined in the object will not be the same.

const obj= {firstname:"Elon", lastname:"Musk", age:50, company:"Tesla"}; 

let ans = ""
for (let key in obj) {
  ans += obj[key] + " ";
}
console.log(ans) // Elon Musk 50 Tesla

we can use for..in with an array but if an order of index matters then don't use it. in this case use for loop, forEach, for..of

3) for...of

for..of will iterate over property value for..in will iterate over the property name

const arr = ['apple', 'orange', 'mango', 'banana']
let ans = "";
for(let i of arr) {
     ans += i + " "
}
console.log(ans) // apple orange mango banana

also, iterate over the string

const string = "Javascript"
let ans = "";
for(let i of string) {
    ans += i + " "
}
console.log(ans) // J a v a s c r i p t

4) while loop while loop through a block of code as long as specified conditions are true. once the condition becomes false it will stop execution and control passes to next statement

const x = 10
white(i < x){
    console.log(i);
    i++;
}
// 1 2 3 4 5 6 7 8 9

if the condition does not become false then it goes into an infinite execution

while(true){
   console.log("Infine loop")
}

5) do...while loop do...while works the same as while just it executes once before it checks the condition.

const x = 5
let i = 0;
do {
   console.log(i);
  i++;
}while(i <= x)
// 0 1 2 3 4 5