JavaScript array reduce start from index -

this problem has been bugging me while , can't seem find answer in web.

is possible use array reduce method starting index?

simple example

var studentgrades = ["john doe", "some school", 6, 7, 8, 7, 9, 9]; 

if need loop on integers in studentgrades, can simple loop

for(var = 2; < studentgrades.length; i++) {   // stuff here ... } 

but let's need average grade sum of integers divided integers count. if array contained integers, there no problem using reduce.

var onlyintegersarr = [5,2,3,4]; var averagegrade = onlyintegersarr.reduce(function(a,b){   return + b; }) / onlyintegersarr.length; 

however if know whatever reasons need skip first 2 array elements , start index array[2].

so example apply reduce studentgrades, starting index studentgrades[2].

is possible reduce?

thank solutions, slice approach, prefer not using new method in case.

e.g.

var average = studentgrades.reduce(function(a,b,i){   return >= 2 ? a+b : 0; }) / (studentgrades.length - 2); 

reduce's 3rd argument index, here fiddle

var averagegrade = onlyintegersarr.reduce(function (a, b, c) {     if (c >= 2) {         return + b;     } else {         return 0;     } }); 

if array has more non-numeric items after second index check fiddle

var studentgrades = ["john doe", "some school", 6, 7, 8, 7, 9, 9, "some school"]; var averagegrade = studentgrades.reduce(function (a, b, c) {     if (c >= 2 && !isnan(b)) {         return + b;     } else if (c >= 2) {         return + 0;     } else {         return 0;     } }) alert(averagegrade);