The While Loop

while (condition) {
    code block to be executed
}

while (i < 10) {
    text += "The number is " + i;
    i++;
}

var cars = ["BMW", "Volvo", "Saab", "Ford"];
var i = 0;
var text = "";

while (cars[i]) {
    text += cars[i] + "<br>";
    i++;
}

The Do/While Loop

do {
    code block to be executed
}
while (condition);

do {
    text += "The number is " + i;
    i++;
}
while (i < 10);

The For Loop

for (statement 1; statement 2; statement 3) {
    code block to be executed
}

for (i = 0; i < 5; i++) {
    text += "The number is " + i + "<br>";
}

The For/In Loop

var person = {fname:"John", lname:"Doe", age:25}; 

var text = "";
var x;
for (x in person) {
    text += person[x];
}