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What is an Immediately Invoked Function in JavaScript? |
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Answer» An Immediately Invoked Function ( known as IIFE and pronounced as IIFY) is a function that runs as soon as it is defined. Syntax of IIFE : (function(){// Do something; })(); To understand IIFE, we need to understand the two sets of parentheses that are added while creating an IIFE : //Do something; }) While executing javascript code, whenever the compiler sees the word “function”, it assumes that we are declaring a function in the code. Therefore, if we do not use the first set of parentheses, the compiler throws an error because it thinks we are declaring a function, and by the syntax of declaring a function, a function should always have a name. function() {//Do something; } // Compiler gives an error since the syntax of declaring a function is wrong in the code above. To remove this error, we add the first set of parenthesis that tells the compiler that the function is not a function declaration, instead, it’s a function expression. //Do something; })(); From the definition of an IIFE, we know that our code should run as soon as it is defined. A function runs only when it is invoked. If we do not invoke the function, the function declaration is returned: (function (){// Do something; }) // Returns the function declaration Therefore to invoke the function, we use the second set of parenthesis. |
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