[cs4] array.indexOf([1,2]) = -1?

sure its been asked before but I cannot find it via google or forum search.

So i have a 2d array.
ar1[0]=[1,2]
ar1[1]=[3,4]

this doesn’t work obviously

ar1.indexOf([1,2]);
neither does any version of that i can think of using quotes, parentheses etc. tryed casting as well.

this returns false
if (ar1[0]===“1,2”)

this returns true
if (ar1[0]==“1,2”)

im assuming the strict equailty is what causes the first to fail. Is there a clean workaround? am i missing something? or is this just not possible?