function extendTraces(gd, update, indices, maxPoints) {
    gd = Lib.getGraphDiv(gd);

    function updateArray(target, insert, maxp) {
        var newArray, remainder;

        if(Lib.isTypedArray(target)) {
            if(maxp < 0) {
                var none = new target.constructor(0);
                var both = concatTypedArray(target, insert);

                if(maxp < 0) {
                    newArray = both;
                    remainder = none;
                } else {
                    newArray = none;
                    remainder = both;
                }
            } else {
                newArray = new target.constructor(maxp);
                remainder = new target.constructor(target.length + insert.length - maxp);

                if(maxp === insert.length) {
                    newArray.set(insert);
                    remainder.set(target);
                } else if(maxp < insert.length) {
                    var numberOfItemsFromInsert = insert.length - maxp;

                    newArray.set(insert.subarray(numberOfItemsFromInsert));
                    remainder.set(target);
                    remainder.set(insert.subarray(0, numberOfItemsFromInsert), target.length);
                } else {
                    var numberOfItemsFromTarget = maxp - insert.length;
                    var targetBegin = target.length - numberOfItemsFromTarget;

                    newArray.set(target.subarray(targetBegin));
                    newArray.set(insert, numberOfItemsFromTarget);
                    remainder.set(target.subarray(0, targetBegin));
                }
            }
        } else {
            newArray = target.concat(insert);
            remainder = (maxp >= 0 && maxp < newArray.length) ?
                newArray.splice(0, newArray.length - maxp) :
                [];
        }

        return [newArray, remainder];
    }

    var undo = spliceTraces(gd, update, indices, maxPoints, updateArray);
    var promise = exports.redraw(gd);
    var undoArgs = [gd, undo.update, indices, undo.maxPoints];
    Queue.add(gd, exports.prependTraces, undoArgs, extendTraces, arguments);

    return promise;
}
extend && prepend traces at indices with update arrays, window trace lengths to maxPoints

Extend and Prepend have identical APIs. Prepend inserts an array at the head while Extend
inserts an array off the tail. Prepend truncates the tail of the array - counting maxPoints
from the head, whereas Extend truncates the head of the array, counting backward maxPoints
from the tail.

If maxPoints is undefined, nonNumeric, negative or greater than extended trace length no
truncation / windowing will be performed. If its zero, well the whole trace is truncated.

@param {Object|HTMLDivElement} gd The graph div
@param {Object} update The key:array map of target attributes to extend
@param {Number|Number[]} indices The locations of traces to be extended
@param {Number|Object} [maxPoints] Number of points for trace window after lengthening.