--- /dev/null
+var baseEach = require('./baseEach');
+
+/**
+ * Gets the extremum value of `collection` invoking `iteratee` for each value
+ * in `collection` to generate the criterion by which the value is ranked.
+ * The `iteratee` is invoked with three arguments: (value, index|key, collection).
+ *
+ * @private
+ * @param {Array|Object|string} collection The collection to iterate over.
+ * @param {Function} iteratee The function invoked per iteration.
+ * @param {Function} comparator The function used to compare values.
+ * @param {*} exValue The initial extremum value.
+ * @returns {*} Returns the extremum value.
+ */
+function baseExtremum(collection, iteratee, comparator, exValue) {
+ var computed = exValue,
+ result = computed;
+
+ baseEach(collection, function(value, index, collection) {
+ var current = +iteratee(value, index, collection);
+ if (comparator(current, computed) || (current === exValue && current === result)) {
+ computed = current;
+ result = value;
+ }
+ });
+ return result;
+}
+
+module.exports = baseExtremum;