add hw2

node_modules/lodash-es/bindKey.js

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+import baseRest from './_baseRest.js';
+import createWrap from './_createWrap.js';
+import getHolder from './_getHolder.js';
+import replaceHolders from './_replaceHolders.js';
+
+/** Used to compose bitmasks for function metadata. */
+var WRAP_BIND_FLAG = 1,
+    WRAP_BIND_KEY_FLAG = 2,
+    WRAP_PARTIAL_FLAG = 32;
+
+/**
+ * Creates a function that invokes the method at `object[key]` with `partials`
+ * prepended to the arguments it receives.
+ *
+ * This method differs from `_.bind` by allowing bound functions to reference
+ * methods that may be redefined or don't yet exist. See
+ * [Peter Michaux's article](http://peter.michaux.ca/articles/lazy-function-definition-pattern)
+ * for more details.
+ *
+ * The `_.bindKey.placeholder` value, which defaults to `_` in monolithic
+ * builds, may be used as a placeholder for partially applied arguments.
+ *
+ * @static
+ * @memberOf _
+ * @since 0.10.0
+ * @category Function
+ * @param {Object} object The object to invoke the method on.
+ * @param {string} key The key of the method.
+ * @param {...*} [partials] The arguments to be partially applied.
+ * @returns {Function} Returns the new bound function.
+ * @example
+ *
+ * var object = {
+ *   'user': 'fred',
+ *   'greet': function(greeting, punctuation) {
+ *     return greeting + ' ' + this.user + punctuation;
+ *   }
+ * };
+ *
+ * var bound = _.bindKey(object, 'greet', 'hi');
+ * bound('!');
+ * // => 'hi fred!'
+ *
+ * object.greet = function(greeting, punctuation) {
+ *   return greeting + 'ya ' + this.user + punctuation;
+ * };
+ *
+ * bound('!');
+ * // => 'hiya fred!'
+ *
+ * // Bound with placeholders.
+ * var bound = _.bindKey(object, 'greet', _, '!');
+ * bound('hi');
+ * // => 'hiya fred!'
+ */
+var bindKey = baseRest(function(object, key, partials) {
+  var bitmask = WRAP_BIND_FLAG | WRAP_BIND_KEY_FLAG;
+  if (partials.length) {
+    var holders = replaceHolders(partials, getHolder(bindKey));
+    bitmask |= WRAP_PARTIAL_FLAG;
+  }
+  return createWrap(key, bitmask, object, partials, holders);
+});
+
+// Assign default placeholders.
+bindKey.placeholder = {};
+
+export default bindKey;