more work

node_modules/lodash/internal/createAssigner.js

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+var bindCallback = require('./bindCallback'),
+    isIterateeCall = require('./isIterateeCall'),
+    restParam = require('../function/restParam');
+
+/**
+ * Creates a function that assigns properties of source object(s) to a given
+ * destination object.
+ *
+ * **Note:** This function is used to create `_.assign`, `_.defaults`, and `_.merge`.
+ *
+ * @private
+ * @param {Function} assigner The function to assign values.
+ * @returns {Function} Returns the new assigner function.
+ */
+function createAssigner(assigner) {
+  return restParam(function(object, sources) {
+    var index = -1,
+        length = object == null ? 0 : sources.length,
+        customizer = length > 2 && sources[length - 2],
+        guard = length > 2 && sources[2],
+        thisArg = length > 1 && sources[length - 1];
+
+    if (typeof customizer == 'function') {
+      customizer = bindCallback(customizer, thisArg, 5);
+      length -= 2;
+    } else {
+      customizer = typeof thisArg == 'function' ? thisArg : null;
+      length -= (customizer ? 1 : 0);
+    }
+    if (guard && isIterateeCall(sources[0], sources[1], guard)) {
+      customizer = length < 3 ? null : customizer;
+      length = 1;
+    }
+    while (++index < length) {
+      var source = sources[index];
+      if (source) {
+        assigner(object, source, customizer);
+      }
+    }
+    return object;
+  });
+}
+
+module.exports = createAssigner;