Coerce findLastIndex and lastIndexOf fromIndex parameter to integer (#4440)

* Enable lastIndexOf, findLast and findLastIndex

* Coerce findLastIndex fromIndex parameter to integer

* Coerce lastIndexOf fromIndex parameter to integer

findLastIndex.js

@@ -1,4 +1,5 @@
 import baseFindIndex from './.internal/baseFindIndex.js'
+import toInteger from './toInteger.js'
 
 /**
  * This method is like `findIndex` except that it iterates over elements
@@ -29,9 +30,10 @@ function findLastIndex(array, predicate, fromIndex) {
   }
   let index = length - 1
   if (fromIndex !== undefined) {
+    index = toInteger(fromIndex)
     index = fromIndex < 0
-      ? Math.max(length + fromIndex, 0)
-      : Math.min(fromIndex, length - 1)
+      ? Math.max(length + index, 0)
+      : Math.min(index, length - 1)
   }
   return baseFindIndex(array, predicate, index, true)
 }

lastIndexOf.js

@@ -1,6 +1,7 @@
 import baseFindIndex from './.internal/baseFindIndex.js'
 import baseIsNaN from './.internal/baseIsNaN.js'
 import strictLastIndexOf from './.internal/strictLastIndexOf.js'
+import toInteger from './toInteger.js'
 
 /**
  * This method is like `indexOf` except that it iterates over elements of
@@ -28,6 +29,7 @@ function lastIndexOf(array, value, fromIndex) {
   }
   let index = length
   if (fromIndex !== undefined) {
+    index = toInteger(fromIndex)
     index = index < 0 ? Math.max(length + index, 0) : Math.min(index, length - 1)
   }
   return value === value

test/findLastIndex-and-lastIndexOf.test.js

@@ -1,11 +1,18 @@
 import assert from 'assert';
 import lodashStable from 'lodash';
-import { _, identity, stubZero, falsey } from './utils.js';
+import { identity, stubZero, falsey } from './utils.js';
+import findLastIndex from '../findLastIndex.js';
+import lastIndexOf from '../lastIndexOf.js';
+
+const methods = {
+  findLastIndex,
+  lastIndexOf
+};
 
 describe('findLastIndex and lastIndexOf', function() {
   lodashStable.each(['findLastIndex', 'lastIndexOf'], function(methodName) {
     var array = [1, 2, 3, 1, 2, 3],
-        func = _[methodName],
+        func = methods[methodName],
         resolve = methodName == 'findLastIndex' ? lodashStable.curry(lodashStable.eq) : identity;
 
     it('`_.' + methodName + '` should return the index of the last matched value', function() {