gistfile1.js

var arr = [1,2,3,4,5,6,7,8];

Array.prototype.divide = function(segments) {
    var response = [];
    var size = Math.floor(this.length/segments);
    for (var i=0;i<segments;i++) {
        var start = i*size;
        var end   = start+size;
        response.push(this.slice(start,end));
    } return response;
};

arr.divide(2); //[[1,2,3,4],[5,6,7,8]]