TypeScript - Loops

Do While - executes at least once - test after the loop

let counter: number = 1;
let output: string = "";
do
{
    output += "<div>" + counter + "</div>";
    counter++;
}
while (counter < 6);

While - tests first and then executes

while (counter < 6)
{
output +="<div>" + counter + "</div>";
counter++;
}

For In - loops thru items in a collection and returns the INDEX

There is no for each in javascript - at least not any more. It was deprecated as of ES4. Use for in instead.

Both for..of and for..in statements iterate over lists. The values iterated on are different though. for..in returns a list of keys (indexes) on the object being iterated, whereas for..of returns a list of values of the numeric properties of the object being iterated.

for in

// show the indexes
let colors : object = [ "Red", "Blue", "White", "Green" ];
let output : string = "";

for (let i in colors)
{
output += i + "<br />";
}

for of - loops through the values of an iterable object.

// show the values
let colors = ["Red", "Blue", "White", "Green"];
let output: string = "";

for (let i of colors)
{
    output += i + "<br />";
}

For - loops thru block of code n number of times

// ITI = Initialize. Test, Increment
var output : string = "";
for (var i = 0; i < 5; i++)
{
    output += "The number is " + i + "<br />";
}