First-class function in js

firstClassFunctionDemo.js

/* #1. Assign the function to a variable */
let functionVar = function() {
  console.log('Hello World!')
}
functionVar();

/* #2. Update function variable */
functionVar = () => {
  console.log(`Hello World Updated!`)
}
functionVar();

/* #3. Pass function as an argument */
let executeFunction = (fnArg)=>{
  fnArg();
}
executeFunction(()=>{console.log(`Hello World from Function Argument`)}); // this will in turn execute the function passed an argument

/* #4. Returning function as return value */
let returnAFunction = ()=>{
  return ()=>{
    console.log(`Hello World from Function return value`)
  }
}
// execute like below
returnAFunction()();