IIEF in modern JS

In modern JavaScript there is one rarely seen feature IIFE. Once before ES6, it was heavily used for module encapsulation.

In my opinion there is actually one nice use for the trusty old IIFE even today when functional style has become popular - converting imperative statements to an expressions!

A statement is a complete instruction that tells the computer to perform an action. It does not necessarily return a value.

    if (x > 5) {  // Conditional statement
        console.log("x is greater than 5");  // Print statement
    }    

An expression is any valid combination of values, variables, operators, and function calls that produces a value.

   const result = x * y + z;   

In functional programming statements are less common because this style emphasizes pure functions and immutability. It is all about evaluating expressions to produce values.

One cool trick that Javascript allows, is to use IIFEs to skip mutable variables.

//using imperative style 
    let result;
    if (x < 0) result = "small";
    if (x === 0) result = "mid";
    if (x > 0) result = "big";

//using functional style 
   const result = (() => {
    if (x < 0) return "small";
    if (x === 0) return "mid";
    if (x > 0) return "big";
   })()