JS: using if/else statements for Duplicate numbers [closed]

Write a function which receives an array and only prints the values that repeat.

For example, given the following array and index, the function will print in console '6,23,33,100'.

var array = [3,6,67,6,23,11,100,8,93,0,17,24,7,1,33,45,28,33,23,12,99,100]; 

I need to use if/else statements