The purpose of a self-executing is that those variables declared in the self-executing function are only available inside the self-executing function.
Variables declared in the self-executing function are, by default, only available to code within the self-executing function.
It is an immediately invoked function expression (IIFE). It is a function, which executes on creation.
Syntax
Here is the syntax −
(function() {
// code
})();As you can see above, the following pair of parentheses converts the code inside the parentheses into an expression:
function(){...}In addition, the next pair, i.e. the second pair of parentheses continues the operation. It calls the function, which resulted from the expression above.