update Array#flatten and Array#flatMap

- use `isArray` instead of `isConcatSpreadable`
- set the target length explicitly

Author: zloirock

client/core.js

@@ -3587,28 +3587,20 @@ module.exports = function (it) {
 
 // https://tc39.github.io/proposal-flatMap/#sec-FlattenIntoArray
 var isArray = __webpack_require__(51);
-var isObject = __webpack_require__(4);
 var toLength = __webpack_require__(8);
 var ctx = __webpack_require__(18);
-var IS_CONCAT_SPREADABLE = __webpack_require__(5)('isConcatSpreadable');
 
 function flattenIntoArray(target, original, source, sourceLen, start, depth, mapper, thisArg) {
   var targetIndex = start;
   var sourceIndex = 0;
   var mapFn = mapper ? ctx(mapper, thisArg, 3) : false;
-  var element, spreadable;
+  var element;
 
   while (sourceIndex < sourceLen) {
     if (sourceIndex in source) {
       element = mapFn ? mapFn(source[sourceIndex], sourceIndex, original) : source[sourceIndex];
 
-      spreadable = false;
-      if (isObject(element)) {
-        spreadable = element[IS_CONCAT_SPREADABLE];
-        spreadable = spreadable !== undefined ? !!spreadable : isArray(element);
-      }
-
-      if (spreadable && depth > 0) {
+      if (isArray(element) && depth > 0) {
         targetIndex = flattenIntoArray(target, original, element, toLength(element.length), targetIndex, depth - 1) - 1;
       } else {
         if (targetIndex >= 0x1fffffffffffff) throw TypeError();
@@ -7134,7 +7126,7 @@ $export($export.P, 'Array', {
     aFunction(callbackfn);
     sourceLen = toLength(O.length);
     A = arraySpeciesCreate(O, 0);
-    flattenIntoArray(A, O, O, sourceLen, 0, 1, callbackfn, arguments[1]);
+    A.length = flattenIntoArray(A, O, O, sourceLen, 0, 1, callbackfn, arguments[1]);
     return A;
   }
 });
@@ -7162,7 +7154,7 @@ $export($export.P, 'Array', {
     var O = toObject(this);
     var sourceLen = toLength(O.length);
     var A = arraySpeciesCreate(O, 0);
-    flattenIntoArray(A, O, O, sourceLen, 0, depthArg === undefined ? 1 : toInteger(depthArg));
+    A.length = flattenIntoArray(A, O, O, sourceLen, 0, depthArg === undefined ? 1 : toInteger(depthArg));
     return A;
   }
 });

client/core.min.js

@@ -1,28 +1,20 @@
 'use strict';
 // https://tc39.github.io/proposal-flatMap/#sec-FlattenIntoArray
 var isArray = require('./_is-array');
-var isObject = require('./_is-object');
 var toLength = require('./_to-length');
 var ctx = require('./_ctx');
-var IS_CONCAT_SPREADABLE = require('./_wks')('isConcatSpreadable');
 
 function flattenIntoArray(target, original, source, sourceLen, start, depth, mapper, thisArg) {
   var targetIndex = start;
   var sourceIndex = 0;
   var mapFn = mapper ? ctx(mapper, thisArg, 3) : false;
-  var element, spreadable;
+  var element;
 
   while (sourceIndex < sourceLen) {
     if (sourceIndex in source) {
       element = mapFn ? mapFn(source[sourceIndex], sourceIndex, original) : source[sourceIndex];
 
-      spreadable = false;
-      if (isObject(element)) {
-        spreadable = element[IS_CONCAT_SPREADABLE];
-        spreadable = spreadable !== undefined ? !!spreadable : isArray(element);
-      }
-
-      if (spreadable && depth > 0) {
+      if (isArray(element) && depth > 0) {
         targetIndex = flattenIntoArray(target, original, element, toLength(element.length), targetIndex, depth - 1) - 1;
       } else {
         if (targetIndex >= 0x1fffffffffffff) throw TypeError();

client/core.min.js.map

@@ -14,7 +14,7 @@ $export($export.P, 'Array', {
     aFunction(callbackfn);
     sourceLen = toLength(O.length);
     A = arraySpeciesCreate(O, 0);
-    flattenIntoArray(A, O, O, sourceLen, 0, 1, callbackfn, arguments[1]);
+    A.length = flattenIntoArray(A, O, O, sourceLen, 0, 1, callbackfn, arguments[1]);
     return A;
   }
 });

library/modules/_flatten-into-array.js

@@ -13,7 +13,7 @@ $export($export.P, 'Array', {
     var O = toObject(this);
     var sourceLen = toLength(O.length);
     var A = arraySpeciesCreate(O, 0);
-    flattenIntoArray(A, O, O, sourceLen, 0, depthArg === undefined ? 1 : toInteger(depthArg));
+    A.length = flattenIntoArray(A, O, O, sourceLen, 0, depthArg === undefined ? 1 : toInteger(depthArg));
     return A;
   }
 });

library/modules/esnext.array.flat-map.js

@@ -1,28 +1,20 @@
 'use strict';
 // https://tc39.github.io/proposal-flatMap/#sec-FlattenIntoArray
 var isArray = require('./_is-array');
-var isObject = require('./_is-object');
 var toLength = require('./_to-length');
 var ctx = require('./_ctx');
-var IS_CONCAT_SPREADABLE = require('./_wks')('isConcatSpreadable');
 
 function flattenIntoArray(target, original, source, sourceLen, start, depth, mapper, thisArg) {
   var targetIndex = start;
   var sourceIndex = 0;
   var mapFn = mapper ? ctx(mapper, thisArg, 3) : false;
-  var element, spreadable;
+  var element;
 
   while (sourceIndex < sourceLen) {
     if (sourceIndex in source) {
       element = mapFn ? mapFn(source[sourceIndex], sourceIndex, original) : source[sourceIndex];
 
-      spreadable = false;
-      if (isObject(element)) {
-        spreadable = element[IS_CONCAT_SPREADABLE];
-        spreadable = spreadable !== undefined ? !!spreadable : isArray(element);
-      }
-
-      if (spreadable && depth > 0) {
+      if (isArray(element) && depth > 0) {
         targetIndex = flattenIntoArray(target, original, element, toLength(element.length), targetIndex, depth - 1) - 1;
       } else {
         if (targetIndex >= 0x1fffffffffffff) throw TypeError();

library/modules/esnext.array.flatten.js

@@ -14,7 +14,7 @@ $export($export.P, 'Array', {
     aFunction(callbackfn);
     sourceLen = toLength(O.length);
     A = arraySpeciesCreate(O, 0);
-    flattenIntoArray(A, O, O, sourceLen, 0, 1, callbackfn, arguments[1]);
+    A.length = flattenIntoArray(A, O, O, sourceLen, 0, 1, callbackfn, arguments[1]);
     return A;
   }
 });

modules/_flatten-into-array.js

@@ -13,7 +13,7 @@ $export($export.P, 'Array', {
     var O = toObject(this);
     var sourceLen = toLength(O.length);
     var A = arraySpeciesCreate(O, 0);
-    flattenIntoArray(A, O, O, sourceLen, 0, depthArg === undefined ? 1 : toInteger(depthArg));
+    A.length = flattenIntoArray(A, O, O, sourceLen, 0, depthArg === undefined ? 1 : toInteger(depthArg));
     return A;
   }
 });