.AS File Format – Statements

All statements and directives

if … else

if (condition) statement [else statement]

The condition is converted to Boolean. There is no elseif keyword; else if chains are an if inside the else.

if (score > best) {
    best = score;
} else if (score == best) {
    tie = true;
} else {
    tie = false;
}

switch

switch (expression) {
    case value: statements
    …
    default: statements
}

The expression is compared with each case value in turn using strict equality (===), and control jumps to the first that matches, or to default. Case values can be any expression, including strings. Control falls through into the next case unless break, return or throw ends it.

switch (event.keyCode) {
    case Keyboard.LEFT:
    case Keyboard.A:
        dx = -1;
        break;
    case Keyboard.RIGHT:
        dx = 1;
        break;
    default:
        dx = 0;
}

while, do … while and for

while (condition) statement
do statement while (condition);
for ([init]; [condition]; [update]) statement

while tests before each pass, do … while after, so its body runs at least once. In for, the init part may declare variables with var; they belong to the enclosing function, not to the loop. Any part can be empty: for (;;) loops until a break.

for (var i:int = 0, n:int = items.length; i < n; i++) {
    process(items[i]);
}

var line:String;
while ((line = reader.next()) != null) {
    lines.push(line);
}

for … in

for ([var] name[:Type] in object) statement

Gives name each enumerable property name of the object in turn, as a string: the indexes of an Array, the keys of an Object or Dictionary (the key objects themselves for a Dictionary), the indexes of an XMLList. Only dynamic properties are visited, never the fixed properties a class declares, and the order is not defined.

for each … in

for each ([var] name[:Type] in object) statement

Gives name each value instead of each name: the elements of an Array or Vector, the property values of an Object or Dictionary, the items of an XMLList. As with for … in, only dynamic properties of an object are visited.

for each (var book:XML in catalogue.book) {
    trace(book.@isbn, book.title);
}

for each (var n:int in new <int>[2, 3, 5]) {
    sum += n;
}

break, continue, labels and return

break [label];
continue [label];
label: statement
return [expression];

• break leaves the innermost loop or switch; with a label, it leaves the labelled statement, which may be any statement or block.
• continue starts the next pass of the innermost loop; with a label, of the labelled loop.
• A label is a name and a colon before a statement. A break without a label cannot be used in a plain block that is not inside a loop or switch.
• return ends the function. In a function typed void it takes no value; in a typed function, strict mode requires a value of that type on every path.

search: for (var row:int = 0; row < rows; row++) {
    for (var col:int = 0; col < cols; col++) {
        if (grid[row][col] == target) {
            found = true;
            break search;
        }
    }
}

with

with (object) statement

Names inside the statement are looked up on object first. An assignment to a name the object does not have goes to the scope outside. It makes code harder to check and to compile efficiently, so it is little used.

with (box.graphics) {
    beginFill(0xFF0000);
    drawRect(0, 0, 100, 50);
    endFill();
}

default xml namespace

default xml namespace = namespaceValue;

Sets the namespace given to unqualified element names in XML literals and searched by unqualified E4X names such as feed.entry. Without it the default is the unnamed namespace (an empty URI). It lasts to the end of the function, like a variable. An XML literal that declares its own default namespace is not affected.

var atom:Namespace = new Namespace("http://www.w3.org/2005/Atom");
default xml namespace = atom;
for each (var entry:XML in feed.entry) {
    trace(entry.title);
}