ArithGeo created by wwebby1 - https://repl.it/E5tx/2

ArithGeo.js

//check if a sequence follows an arithmetic or geometric pattern. return -1 if neither

function ArithGeo(arr) { 
 var arithchecker = false;
 var geochecker = false;
 
 for(var i = 1; i < arr.length; i++)
 {
 	var diff1 = arr[i] - arr[i-1];
 	var diff2 = arr[i+1] - arr[i];
 	if(diff1 == diff2)
 	arithchecker = true;
 	else
 	arithchecker = false;
 	break;
 }
for(var j = 1; j < arr.length; j++){
	var dif1 = arr[j] - arr[j-1];
	var dif2 = arr[j+1] - arr[j]
	var dif3 = arr[j+2] - arr[j+1];
	var ratio1 = dif2/dif1;
	var ratio2 = dif3/dif2;
	if(ratio1 == ratio2)
	geochecker = true;
	else
	geochecker = false;
	break;
}
if(arithchecker===true)
console.log("Arithmetic");
else if(geochecker===true)
console.log("Geometric");
else
console.log(-1);
}
   
// keep this function call here 
ArithGeo([1, 2, 3, 4] ) ;  
ArithGeo([2, 4, 8, 16]);
ArithGeo([1, 3, 6, 9]);