Step by Step solution about How to resolve the algorithm Array concatenation step by step in the JavaScript programming language

The provided source code demonstrates the use of the concat() function to concatenate arrays in JavaScript.

Original Code

var a = [1,2,3],
   b = [4,5,6],
   c = a.concat(b); //=> [1,2,3,4,5,6]

In this code, three variables (a, b, c) are created and assigned values. Variables a and b are arrays containing numbers, and variable c is assigned the result of concatenating arrays a and b using the concat() method. The resulting array c contains all elements from both a and b.

Function Implementation

(function () {
   'use strict';

   // concat :: [[a]] -> [a]
   function concat(xs) {
       return [].concat.apply([], xs);
   }
})();

A self-invoking anonymous function (IIFE) is used to define a function named concat. This function takes a single argument xs, which is expected to be an array of arrays. The purpose of this function is to concatenate all the inner arrays into a single, flattened array.

Inside the concat function, the code uses [].concat.apply([], xs) to achieve concatenation. Here's how it works:

• [].concat is the concat method on an empty array ([]). It is used to concatenate multiple arrays together.
• apply is a method that allows you to call a function with a specific value for this and pass in an array of arguments.
• In this case, apply is used to call the concat method with this set to an empty array ([]) and xs (an array of arrays) as the arguments.

The result of this operation is a single array containing all the elements from all the inner arrays in xs.

Function Invocation

return concat(
   [["alpha", "beta", "gamma"], 
   ["delta", "epsilon", "zeta"], 
   ["eta", "theta", "iota"]]
);

Finally, the concat function is invoked with an array of arrays as its argument. The result is a single array containing all the elements from the inner arrays:

["alpha", "beta", "gamma", "delta", "epsilon", "zeta", "eta", "theta", "iota"]

var a = [1,2,3],
    b = [4,5,6],
    c = a.concat(b); //=> [1,2,3,4,5,6]


(function () {
    'use strict';

    // concat :: [[a]] -> [a]
    function concat(xs) {
        return [].concat.apply([], xs);
    }


   return concat(
      [["alpha", "beta", "gamma"], 
      ["delta", "epsilon", "zeta"], 
      ["eta", "theta", "iota"]]
  );

})();