Javascript function to pre-populate multiple 2D arrays

gistfile1.js

populateEmptyArrays = function(vars, num) {
  //Function to pre-populate multiple 2D arrays
  //vars = Array of variable names to pre-populate with arrays
  //num = Array size
  if(!(vars instanceof Array) || isNaN(num)) return;
  
  for(i in vars) {
    window[vars[i]] = (function(a){ while(a.push([]) < num); return a})([])
  }
}

populateEmptyArrays(['A','B','C'], 6);

console.log(A); //[[], [], [], [], [], []]
console.log(B); //[[], [], [], [], [], []]
console.log(C); //[[], [], [], [], [], []]