Basically Javascript previous version ES5(script 5) support three loops and new version ES6(script 6) version support two more loops i.e for-of loop (ES6 ) and an iterator (ES6) .

1) for each loop
for each() method iterates the specific variables over all the values of object's properties .For each different statement , a specified statement is executed .
Syntax ->

for each ( variable in object ){
//statements;
}

variable -> variable is to iterate the values ,and is declared withe the var keyword , and this variable is local to the function , not to the loop.
object ->object for which the properties are iterated .
statement ->A statements is used to execute for each property . To execute multiple statements within the loop use a block statement ( {.... } ) like this . Example ->
var sum = 0;

var values = { a :5 , b : 10 , c : 15 } ;
for each ( var item in values ){
sum = sum + item ;
}
console.log(sum); // output is -> 30 i.e 5 + 10 +15 .<br><br>

2) for loop
simple for loop is used to create a loop that consists three optional expressions , which comes in paranthesis and separted by semicolons and followed by a statement or multiple statements .
Syntax ->

for( initialize ; , condition ; , final-expression ;){
statement
}

initialize -> In this there is a variable declaration or used to initialize a counter variable. This expression may be optional and declare with the var keyword. These variables are not local to the loop, i.e they are in the same scope .
condition ->
This check the given condition and evaluated before each loop iteration .If this expression is true than the statement will be executed . And this is also a optional .If you omit this expression then the condition always evaluates as a true .
final expression -> This expression is evaluated at the end of each loop iteration. Generally it is used to update or increment the counter variable .
Example ->

for (var i = 0; i < 10 ; i++){
console.log(i); //output ->0 1 2 3 4 5 6 7 8 9
}

Optional for expression -> 1) when initialize expression is not required

var i =0;
for( ; i < 10 ; i++ ){
console.log(i); //output ->0 1 2 3 4 5 6 7 8 9
}

2) when condition expression is not required

 for(var i =0; ; i++ ){
    console.log(i); 
if(i >3) 
break;
    }

3) when all three expression is omit

var i = 0;     
     for(; ;){
        if(i > 3)
        break;
  console.log(i);
  i++;
}