break

break;
break labelname;

Exit from the innermost loop or switch statement or from the statement named by label.

case

case expression:

Label a statement within a switch statement.

continue

continue; 
continue labelname;

Restart the innermost loop or the loop named by label.

default

default: 

Label the default statement within a switch statement.

do/while

do
    statement
while (expression);

An alternative to the while loop.

empty

;

Do nothing.

for

for (initialize ; test ; increment)
    statement

An easy-to-use loop.

for/in

for (variable in object)
    statement

Loop through the properties of an object.

function

function funcname([arg1[..., argn]]) {
    statements
}

Declare a function.

if/else

if (expression)
    statement1
[else statement2]

Conditionally execute code.

label

identifier: statement

Give statement the name identifier.

return

return [expression];

Return from a function or return the value of expression from a function.

switch

switch (expression) {
    statements
}

Multiway branch to statements labeled with case or default: .

throw

throw expression;

Throw an exception.

try

try {
    statements
}
catch (identifier) {
    statements
}
finally {
    statements
}

Catch an exception.

var

var name_1 [ = value_1]
[ ..., name_n [ = value_n]];

Declare and initialize variables.

while

while (expression)
    statement

A basic loop construct.

with

with (object)
    statement

Extend the scope chain. (Deprecated.)