join in array

var fruits = ["Banana", "Orange", "Apple", "Mango"];

var energy = fruits.join();
 

var a = ['Wind', 'Water', 'Fire'];
a.join();      // 'Wind,Water,Fire'
a.join(', ');  // 'Wind, Water, Fire'
a.join(' + '); // 'Wind + Water + Fire'
a.join('');    // 'WindWaterFire'