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I was recently comparing the current version of json2.js with the version I had in my project and noticed a difference in how the function expression was created and self executed.
The code used to wrap an anonymous function in parenthesis and then execute it,
(function () { // code here })(); but now it wraps the auto-executed function in parenthesis.
(function () { // code here }()); There is a comment by CMS in the accepted answer of Explain JavaScript’s encapsulated anonymous function syntax that “both: (function(){})(); and (function(){}()); are valid.”
I was wondering what the difference is? Does the former take up memory by leaving around a global, anonymous function? Where should the parenthesis be located?
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In JavaScript, the functions wrapped with parenthesis are called “Immediately Invoked Function Expressions" or "Self Executing Functions. The purpose of wrapping is to namespace and control the visibility of member functions. It wraps code inside a function scope and decrease clashing with other libraries.
Parenthesis are used in an arrow function to return an object. Parenthesis are used to group multiline of codes on JavaScript return statement so to prevent semicolon inserted automatically in the wrong place.
JavaScript in head: A JavaScript function is placed inside the head section of an HTML page and the function is invoked when a button is clicked. JavaScript in body: A JavaScript function is placed inside the body section of an HTML page and the function is invoked when a button is clicked.
function hello() { alert('Hello world'); } hello(); Anonymous function definition: var anon = function() { alert('I am anonymous'); } anon();
They're virtually the same.
The first wraps parentheses around a function to make it a valid expression and invokes it. The result of the expression is undefined.
The second executes the function and the parentheses around the automatic invocation make it a valid expression. It also evaluates to undefined.
I don't think there's a "right" way of doing it, since the result of the expression is the same.
> function(){}() SyntaxError: Unexpected token ( > (function(){})() undefined > (function(){return 'foo'})() "foo" > (function(){ return 'foo'}()) "foo" If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
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