One possible method.

function stringToArray()
{
myStr="5,6,8,5,6,5,7,6,8";
myArray=myStr.split(",");
for (i=0; i<myArray.length; i++)
{
	myChar=myArray[i];
	if (myChar==""){continue;}
	for (j=i+1; j<myArray.length; j++)
	{
		if (myChar==myArray[j]){myArray[j]=""}
	}
}
myStr="";
for (i=0; i<myArray.length; i++)
	if (myArray[i]!=""){myStr+=myArray[i]}
}

Louis LAFRUIT.