return
As you’ll
recall,
invoking a function with the ( )
operator is an
expression. All expressions have values;
the return
statement is used to specify the value
returned by a function. This value is the value of the function
invocation expression. The syntax of the return
statement is:
return expression
;
A return
statement may appear only within the body
of a function. It is a syntax error for it to appear anywhere else.
When the return
statement is executed,
expression
is evaluated and returned as
the value of the function. Execution of the function stops when the
return
statement is executed, even if there are
other statements remaining in the function body. The
return
statement can be used to return a value
like this:
function square(x) { return x*x; }
The return
statement may also be used without an
expression
to simply terminate execution
of the function without returning a value. For example:
function display_object(obj) { // First make sure our argument is valid // Skip the rest of the function if it is not if (obj == null) return; // Rest of function goes here... }
If a function executes a return
statement with no
expression
, or if it returns because it
reaches the end of the function body, the value of the function call
expression is undefined
.
Because of JavaScript’s automatic semicolon insertion, you may
not include a line break between the return
keyword and the expression that follows it.
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