var node = document.createElement("div");

// Current use-case for Array.isArray()

function setClass( elem, arg ) {

  var className = arg;

  if ( Array.isArray( arg ) ) {
    className = arg.join(" ");
  }

  elem.className = className;

  return elem;
}

// Used as:

setClass( node, [ "ui", "logic", "template" ] );

console.log( node.classList );

setClass( node, "ui" );

console.log( node.classList );




// How would an array prototype method be beneficial?

// Implementation 1:
Array.prototype.isArray = function() {
  return Array.isArray( this );
};

function setClass( elem, arg ) {

  var className = arg;

  if ( [].isArray.call( arg ) ) {
    className = arg.join(" ");
  }

  elem.className = className;

  return elem;
}


// Used as:

setClass( node, [ "ui", "logic", "template" ] );

console.log( node.classList );

setClass( node, "ui" );

console.log( node.classList );




// Implementation 2
Array.prototype.isArray = function( obj ) {
  return Array.isArray( obj );
};

function setClass( elem, arg ) {

  var className = arg;

  if ( [].isArray( arg ) ) {
    className = arg.join(" ");
  }

  elem.className = className;

  return elem;
}


// Used as:

setClass( node, [ "ui", "logic", "template" ] );

console.log( node.classList );

setClass( node, "ui" );

console.log( node.classList );







// Wondering how or why this could be beneficial.