Finding the Largest array

var foo = [1,20,254],i, largest= foo[0];

for(i=1; i<foo.length; i++){
if(foo[i]>largest){
largest = foo[i];
}
}
document.write( "<br /> " +"Largest no is: " + largest);


Hi I Just started programming and write a very small code that is to find the largest value in an Array I want to know the working of this code,The code is working fine for me but actually I want to know how this code work.Mainly i'm confused in largest=foo[0] variable that i declare above.