Coerce drop and dropRight n param using toInteger (#4412)

* Coerce dropRight n param using toInteger

* Coerce drop n param using toInteger

test/drop.test.js

@@ -0,0 +1,62 @@
+import assert from 'assert';
+import lodashStable from 'lodash';
+import { falsey, LARGE_ARRAY_SIZE, isEven } from './utils.js';
+import drop from '../drop.js';
+
+describe('drop', function() {
+  var array = [1, 2, 3];
+
+  it('should drop the first two elements', function() {
+    assert.deepStrictEqual(drop(array, 2), [3]);
+  });
+
+  it('should treat falsey `n` values, except `undefined`, as `0`', function() {
+    var expected = lodashStable.map(falsey, function(value) {
+      return value === undefined ? [2, 3] : array;
+    });
+
+    var actual = lodashStable.map(falsey, function(n) {
+      return drop(array, n);
+    });
+
+    assert.deepStrictEqual(actual, expected);
+  });
+
+  it('should return all elements when `n` < `1`', function() {
+    lodashStable.each([0, -1, -Infinity], function(n) {
+      assert.deepStrictEqual(drop(array, n), array);
+    });
+  });
+
+  it('should return an empty array when `n` >= `length`', function() {
+    lodashStable.each([3, 4, Math.pow(2, 32), Infinity], function(n) {
+      assert.deepStrictEqual(drop(array, n), []);
+    });
+  });
+
+  it('should coerce `n` to an integer', function() {
+    assert.deepStrictEqual(drop(array, 1.6), [2, 3]);
+  });
+
+  it('should work in a lazy sequence', function() {
+    var array = lodashStable.range(1, LARGE_ARRAY_SIZE + 1),
+        predicate = function(value) { values.push(value); return isEven(value); },
+        values = [],
+        actual = _(array).drop(2).drop().value();
+
+    assert.deepEqual(actual, array.slice(3));
+
+    actual = _(array).filter(predicate).drop(2).drop().value();
+    assert.deepEqual(values, array);
+    assert.deepEqual(actual, drop(drop(_.filter(array, predicate), 2)));
+
+    actual = _(array).drop(2).dropRight().drop().dropRight(2).value();
+    assert.deepEqual(actual, _.dropRight(drop(_.dropRight(drop(array, 2))), 2));
+
+    values = [];
+
+    actual = _(array).drop().filter(predicate).drop(2).dropRight().drop().dropRight(2).value();
+    assert.deepEqual(values, array.slice(1));
+    assert.deepEqual(actual, _.dropRight(drop(_.dropRight(drop(_.filter(drop(array), predicate), 2))), 2));
+  });
+});