+ * Returns a new iterator over array, between indexes start and
+ * start + length, and only returns entries that pass the accept function
+ *
+ * @param array the array to iterate over.
+ * @param start the first index to iterate over
+ * @param length the number of elements in the array to iterate over.
+ * This, along with start, defines a slice of the array, and so length
+ * doesn't imply the number of elements in the iterator when accept
+ * doesn't always accept all values.
+ * @param predicate a function that takes parameters array and idx, which
+ * returns true when the element should be returned. If omitted, all
+ * elements are accepted.
+ *
+ * TODO(konigsberg): add default vlues to start and length.
+ */
+Dygraph.createIterator = function(array, start, length, predicate) {
+ var iter = new function() {
+ this.end_ = Math.min(array.length, start + length);
+ this.nextIdx_ = start - 1; // use -1 so initial call to advance works.
+ this.hasNext_ = true;
+ this.peek_ = null;
+ var self = this;
+
+ this.hasNext = function() {
+ return self.hasNext_;
+ }
+
+ this.next = function() {
+ if (self.hasNext_) {
+ var obj = self.peek_;
+ self.advance_();
+ return obj;
+ }
+ return null;
+ }
+ this.peek = function() {
+ return self.peek_;
+ }
+ this.advance_ = function() {
+ var nextIdx = self.nextIdx_;
+ nextIdx++;
+ while(nextIdx < self.end_) {
+ if (!predicate || predicate(array, nextIdx)) {
+ self.peek_ = array[nextIdx];
+ self.nextIdx_ = nextIdx;
+ return;
+ }
+ nextIdx++;
+ }
+ self.nextIdx_ = nextIdx;
+ self.hasNext_ = false;
+ self.peek_ = null;
+ }
+ };
+ iter.advance_();
+ return iter;
+};
+
+/**
+ * @private