For Loops
- You’ll be able to create different kinds of for loop
for
clearly shows the start and end values
is especially good for handling a series of data
(data_structure.length tells you how many items data_structure contains)
<html><head>
<script>
var continents=["Australia", "Africa",
"Antarctica", "Eurasia", "America"];
var response, count=0;
for (var index=0; index < continents.length;
index++) {
response = confirm("Have you been to " +
continents[index] + "?");
if (response) count++;
}
alert("You have been to " + count +
" continents!");
</script>
</head></html>for…in
- gives you the index of each item
<!doctype html>
<html><head>
<script>
var continents=["Australia", "Africa",
"Antarctica", "Eurasia", "America"];
var response, count=0;
for (var index in continents) {
response=confirm("Have you been to "
+ continents[index] + "?");
if (response) count++;
}
alert("You have been to " + count +
" continents!");
</script>
</head></html>- this example shows how for…in can be used to access the content of a data structure(like json).
<!doctype html>
<html><head>
<title>Example of for in</title>
<script>
var response, count=0;
var onePerson = { initials:"DR", age:40,job:"Professor" };
for (var property in onePerson) {
alert(property + "=" + onePerson[property]);
}
</script>
</head></html>for…of
- gives you each item(not index)
<!doctype html>
<html><head>
<title>Example of for of</title>
<script>
var continents=["Australia", "Africa",
"Antarctica", "Eurasia", "America"];
var response, count=0;
for (var continent of continents) {
response = confirm("Have you been to " +
continent + "?");
if (response) count++;
}
alert("You have been to " + count + " continents!");
</script>
</head></html>Loop Control
You’ll be able to control loops in two new ways
break continue
break
- break
totally stops the loop
continue
- continue
stops the current iteration