Immediately-Invoked Function Expression (IIFE) Patterns in JS (v2)

Revision 2 of this benchmark created on

Description

Each of these represents one way of instantiating an IIFE (immediately-invoked function expression, AKA self-invoking function) in JS. (Learn more about IIFEs here.)

» They appear in descending order of popularity.

» The first several use symbolic operators, while the latter several use keywords and statements.

–ck

Test runner

Ready to run.

Testing in
TestOps/sec
Expressive Create-Instance (())
(function () {
})();  // returns implicit undefined

(function () {
   return true;
})();  // returns explicit true

(function (x) {
   var foo = x.toLowerCase();
})('FOO');  // returns implicit undefined
ready
Bitwise NOT (~)
~function () {
}();  // returns implicit -1

~function () {
   return true;
}();  // returns explicit -2

~function (x) {
   var foo = x.toLowerCase();
}('FOO');  // returns implicit -1
ready
Bang/Logical Inversion (!)
!function () {
}();  // returns implicit true

!function () {
   return true;
}();  // returns explicit false

!function (x) {
   var foo = x.toLowerCase();
}('FOO');  // returns implicit true
ready
Unary Sum (+)
+function () {
}();  // returns implicit NaN

+function () {
   return true;
}();  // returns explicit 1

+function (x) {
   var foo = x.toLowerCase();
}('FOO');  // returns explicit NaN
ready
Unary Negation (-)
-function () {
}();  // returns explicit NaN

-function () {
   return true;
}();  // returns explicit -1

-function (x) {
   var foo = x.toLowerCase();
}('FOO');  // returns explicit NaN
ready
Forced Instantial Ternary (?:)
true? function () {
}() :null;  // returns explicit undefined

'foo'? function () {
   return true;
}() :null;  // returns explicit true

'foo'? function (x) {
   var foo = x.toLowerCase();
}('FOO') :null;  // returns explicit undefined
ready
Forced Fallback Ternary (?:)
false? null :function () {
}();  // returns explicit undefined

false? null :function () {
   return true;
}();  // returns explicit true

false? null :function (x) {
   var foo = x.toLowerCase();
}('FOO');  // returns explicit undefined
ready
Indirect Clausal Evaluation by Comma (,)
'', function () {
}();  // returns explicit undefined

'', function () {
   return true;
}();  // returns explicit true

'', function (x) {
   var foo = x.toLowerCase();
}('FOO');  // returns explicit undefined
ready
Faux Constructor (new)
new function () {
}();  // returns explicit [object Object]

new function () {
   return true;
}();  // returns implicit [object Object]

new function (x) {
   var foo = x.toLowerCase();
}('FOO');  // returns implicit [object Object]
ready
Void Operator (void)
void function () {
}();  // returns explicit undefined

void function () {
   return true;
}();  // returns explicit undefined

void function (x) {
   var foo = x.toLowerCase();
}('FOO');  // returns explicit undefined
ready
Contextual Return Statement (return)
return function () {
}();  // returns explicit undefined

return function () {
   return true;
}();  // returns explicit true

return function (x) {
   var foo = x.toLowerCase();
}('FOO');  // returns explicit undefined
ready
Delete Operator (delete)
delete function () {
}();  // returns implicit true

delete function () {
   return true;
}();  // returns implicit true

delete function (x) {
   var foo = x.toLowerCase();
}('FOO');  // returns implicit true

/*
  NOTE: Return values may depend on environment’s adherence to specification. 
*/
ready
Contextual Throw Statement (throw)
throw function () {
}();  // returns falsey exception

throw function () {
   return true;
}();  // returns true exception

throw function (x) {
   var foo = x.toLowerCase();
}('FOO');  // returns falsey exception

/*
  NOTE: Yields an error in JSPerf, but actual performance is similar to Delete Operator method (above).
*/
ready
While
while (function () {
}());  // returns implicit undefined

while (function () {
   return false;
}());  // returns explicit false

while (function (x) {
   var foo = x.toLowerCase();
}('FOO'));  // returns implicit undefined
ready

Revisions

You can edit these tests or add more tests to this page by appending /edit to the URL.