Merge pull request #2134 from jridgewell/ios-jit-isArrayLike

Fix iOS JIT Bug, Part 2

Author: megawac

underscore.js

@@ -122,13 +122,20 @@
     return result;
   };
 
+  var property = function(key) {
+    return function(obj) {
+      return obj == null ? void 0 : obj[key];
+    };
+  };
+
   // Helper for collection methods to determine whether a collection
   // should be iterated as an array or as an object
   // Related: http://people.mozilla.org/~jorendorff/es6-draft.html#sec-tolength
   // Avoids a very nasty iOS 8 JIT bug on ARM-64. #2094
-  var MAX_ARRAY_INDEX = Math.pow(2, 53) - 1, LENGTH = 'length';
+  var MAX_ARRAY_INDEX = Math.pow(2, 53) - 1;
+  var getLength = property('length');
   var isArrayLike = function(collection) {
-    var length = collection != null && collection[LENGTH];
+    var length = getLength(collection);
     return typeof length == 'number' && length >= 0 && length <= MAX_ARRAY_INDEX;
   };
 
@@ -482,7 +489,7 @@
   // Internal implementation of a recursive `flatten` function.
   var flatten = function(input, shallow, strict, startIndex) {
     var output = [], idx = 0;
-    for (var i = startIndex || 0, length = input && input.length; i < length; i++) {
+    for (var i = startIndex || 0, length = getLength(input); i < length; i++) {
       var value = input[i];
       if (isArrayLike(value) && (_.isArray(value) || _.isArguments(value))) {
         //flatten current level of array or arguments object
@@ -513,7 +520,6 @@
   // been sorted, you have the option of using a faster algorithm.
   // Aliased as `unique`.
   _.uniq = _.unique = function(array, isSorted, iteratee, context) {
-    if (array == null) return [];
     if (!_.isBoolean(isSorted)) {
       context = iteratee;
       iteratee = isSorted;
@@ -522,7 +528,7 @@
     if (iteratee != null) iteratee = cb(iteratee, context);
     var result = [];
     var seen = [];
-    for (var i = 0, length = array.length; i < length; i++) {
+    for (var i = 0, length = getLength(array); i < length; i++) {
       var value = array[i],
           computed = iteratee ? iteratee(value, i, array) : value;
       if (isSorted) {
@@ -549,10 +555,9 @@
   // Produce an array that contains every item shared between all the
   // passed-in arrays.
   _.intersection = function(array) {
-    if (array == null) return [];
     var result = [];
     var argsLength = arguments.length;
-    for (var i = 0, length = array.length; i < length; i++) {
+    for (var i = 0, length = getLength(array); i < length; i++) {
       var item = array[i];
       if (_.contains(result, item)) continue;
       for (var j = 1; j < argsLength; j++) {
@@ -581,7 +586,7 @@
   // Complement of _.zip. Unzip accepts an array of arrays and groups
   // each array's elements on shared indices
   _.unzip = function(array) {
-    var length = array && _.max(array, 'length').length || 0;
+    var length = array && _.max(array, getLength).length || 0;
     var result = Array(length);
 
     for (var index = 0; index < length; index++) {
@@ -595,7 +600,7 @@
   // the corresponding values.
   _.object = function(list, values) {
     var result = {};
-    for (var i = 0, length = list && list.length; i < length; i++) {
+    for (var i = 0, length = getLength(list); i < length; i++) {
       if (values) {
         result[list[i]] = values[i];
       } else {
@@ -609,7 +614,7 @@
   function createPredicateIndexFinder(dir) {
     return function(array, predicate, context) {
       predicate = cb(predicate, context);
-      var length = array != null && array.length;
+      var length = getLength(array);
       var index = dir > 0 ? 0 : length - 1;
       for (; index >= 0 && index < length; index += dir) {
         if (predicate(array[index], index, array)) return index;
@@ -627,7 +632,7 @@
   _.sortedIndex = function(array, obj, iteratee, context) {
     iteratee = cb(iteratee, context, 1);
     var value = iteratee(obj);
-    var low = 0, high = array.length;
+    var low = 0, high = getLength(array);
     while (low < high) {
       var mid = Math.floor((low + high) / 2);
       if (iteratee(array[mid]) < value) low = mid + 1; else high = mid;
@@ -638,7 +643,7 @@
   // Generator function to create the indexOf and lastIndexOf functions
   function createIndexFinder(dir, predicateFind, sortedIndex) {
     return function(array, item, idx) {
-      var i = 0, length = array ? array.length : -1;
+      var i = 0, length = getLength(array);
       if (typeof idx == 'number') {
         if (dir > 0) {
             i = idx >= 0 ? idx : Math.max(idx + length, i);
@@ -1136,7 +1141,7 @@
     }
     // Assume equality for cyclic structures. The algorithm for detecting cyclic
     // structures is adapted from ES 5.1 section 15.12.3, abstract operation `JO`.
-    
+
     // Initializing stack of traversed objects.
     // It's done here since we only need them for objects and arrays comparison.
     aStack = aStack || [];
@@ -1287,11 +1292,7 @@
 
   _.noop = function(){};
 
-  _.property = function(key) {
-    return function(obj) {
-      return obj == null ? void 0 : obj[key];
-    };
-  };
+  _.property = property;
 
   // Generates a function for a given object that returns a given property.
   _.propertyOf = function(obj) {
@@ -1300,7 +1301,7 @@
     };
   };
 
-  // Returns a predicate for checking whether an object has a given set of 
+  // Returns a predicate for checking whether an object has a given set of
   // `key:value` pairs.
   _.matcher = _.matches = function(attrs) {
     attrs = _.extendOwn({}, attrs);
@@ -1527,7 +1528,7 @@
   // Provide unwrapping proxy for some methods used in engine operations
   // such as arithmetic and JSON stringification.
   _.prototype.valueOf = _.prototype.toJSON = _.prototype.value;
-  
+
   _.prototype.toString = function() {
     return '' + this._wrapped;
   };