diff --git a/CHANGELOG.md b/CHANGELOG.md
index 9f3128b6..64ef716b 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,13 @@
 # jsonld ChangeLog
 
+## 8.1.1 - 2023-02-dd
+
+### Fixed
+- Improved `types.isObject` internal API performance.
+- Improved `graphTypes.*` internal API performance.
+- Improved `util.addValue` performance.
+- Improved `util.compareValues` performance.
+
 ## 8.1.0 - 2022-08-29
 
 ### Fixed
diff --git a/README.md b/README.md
index 045325a4..dd7c372e 100644
--- a/README.md
+++ b/README.md
@@ -476,7 +476,7 @@ Use a command line with a test suite and a benchmark flag:
 EARL reports with benchmark data can be generated with an optional environment
 details:
 
-    JSONLD_TESTS=`pwd`/../json-ld.org/benchmarks/b001-manifiest.jsonld JSONLD_BENCHMARK=1 EARL=earl-test.jsonld TEST_ENV=1 npm test
+    JSONLD_TESTS=`pwd`/../json-ld.org/benchmarks/b001-manifest.jsonld JSONLD_BENCHMARK=1 EARL=earl-test.jsonld TEST_ENV=1 npm test
 
 See `tests/test.js` for more `TEST_ENV` control and options.
 
diff --git a/lib/graphTypes.js b/lib/graphTypes.js
index 3d06d6cf..ac8ca410 100644
--- a/lib/graphTypes.js
+++ b/lib/graphTypes.js
@@ -1,5 +1,5 @@
-/*
- * Copyright (c) 2017 Digital Bazaar, Inc. All rights reserved.
+/*!
+ * Copyright (c) 2017-2023 Digital Bazaar, Inc. All rights reserved.
  */
 'use strict';
 
@@ -52,7 +52,7 @@ api.isValue = v =>
   // Note: A value is a @value if all of these hold true:
   // 1. It is an Object.
   // 2. It has the @value property.
-  types.isObject(v) && ('@value' in v);
+  types.isObject(v) && v['@value'] !== undefined;
 
 /**
  * Returns true if the given value is a @list.
@@ -65,7 +65,7 @@ api.isList = v =>
   // Note: A value is a @list if all of these hold true:
   // 1. It is an Object.
   // 2. It has the @list property.
-  types.isObject(v) && ('@list' in v);
+  types.isObject(v) && v['@list'] !== undefined;
 
 /**
  * Returns true if the given value is a @graph.
@@ -78,7 +78,7 @@ api.isGraph = v => {
   // 2. It has an `@graph` key.
   // 3. It may have '@id' or '@index'
   return types.isObject(v) &&
-    '@graph' in v &&
+    v['@graph'] !== undefined &&
     Object.keys(v)
       .filter(key => key !== '@id' && key !== '@index').length === 1;
 };
@@ -93,7 +93,7 @@ api.isSimpleGraph = v => {
   // 1. It is an object.
   // 2. It has an `@graph` key.
   // 3. It has only 1 key or 2 keys where one of them is `@index`.
-  return api.isGraph(v) && !('@id' in v);
+  return api.isGraph(v) && v['@id'] === undefined;
 };
 
 /**
@@ -109,12 +109,13 @@ api.isBlankNode = v => {
   // 2. If it has an @id key that is not a string OR begins with '_:'.
   // 3. It has no keys OR is not a @value, @set, or @list.
   if(types.isObject(v)) {
-    if('@id' in v) {
-      const id = v['@id'];
+    const id = v['@id'];
+    if(id !== undefined) {
       return !types.isString(id) || id.indexOf('_:') === 0;
     }
-    return (Object.keys(v).length === 0 ||
-      !(('@value' in v) || ('@set' in v) || ('@list' in v)));
+    return (v['@value'] === undefined &&
+      v['@set'] === undefined &&
+      v['@list'] === undefined) || Object.keys(v).length === 0;
   }
   return false;
 };
diff --git a/lib/nodeMap.js b/lib/nodeMap.js
index 9e61d5e0..e62c957b 100644
--- a/lib/nodeMap.js
+++ b/lib/nodeMap.js
@@ -201,6 +201,7 @@ api.createNodeMap = (input, graphs, graph, issuer, name, list) => {
           {propertyIsArray: true, allowDuplicate: false});
         api.createNodeMap(o, graphs, graph, issuer, id);
       } else if(graphTypes.isValue(o)) {
+        // handle @value
         util.addValue(
           subject, property, o,
           {propertyIsArray: true, allowDuplicate: false});
@@ -213,7 +214,7 @@ api.createNodeMap = (input, graphs, graph, issuer, name, list) => {
           subject, property, o,
           {propertyIsArray: true, allowDuplicate: false});
       } else {
-        // handle @value
+        // handle remaining cases
         api.createNodeMap(o, graphs, graph, issuer, name);
         util.addValue(
           subject, property, o, {propertyIsArray: true, allowDuplicate: false});
diff --git a/lib/types.js b/lib/types.js
index d07e4fa1..38cc4402 100644
--- a/lib/types.js
+++ b/lib/types.js
@@ -1,5 +1,5 @@
-/*
- * Copyright (c) 2017 Digital Bazaar, Inc. All rights reserved.
+/*!
+ * Copyright (c) 2017-2023 Digital Bazaar, Inc. All rights reserved.
  */
 'use strict';
 
@@ -70,7 +70,7 @@ api.isNumeric = v => !isNaN(parseFloat(v)) && isFinite(v);
  *
  * @return true if the value is an Object, false if not.
  */
-api.isObject = v => Object.prototype.toString.call(v) === '[object Object]';
+api.isObject = v => v !== null && typeof v === 'object' && !Array.isArray(v);
 
 /**
  * Returns true if the given value is a String.
diff --git a/lib/util.js b/lib/util.js
index 57bf9f74..f4c8820f 100644
--- a/lib/util.js
+++ b/lib/util.js
@@ -1,5 +1,5 @@
-/*
- * Copyright (c) 2017-2019 Digital Bazaar, Inc. All rights reserved.
+/*!
+ * Copyright (c) 2017-2023 Digital Bazaar, Inc. All rights reserved.
  */
 'use strict';
 
@@ -191,7 +191,7 @@ api.validateTypeValue = (v, isFrame) => {
 api.hasProperty = (subject, property) => {
   if(subject.hasOwnProperty(property)) {
     const value = subject[property];
-    return (!types.isArray(value) || value.length > 0);
+    return !types.isArray(value) || value.length > 0;
   }
   return false;
 };
@@ -206,24 +206,16 @@ api.hasProperty = (subject, property) => {
  * @return true if the value exists, false if not.
  */
 api.hasValue = (subject, property, value) => {
-  if(api.hasProperty(subject, property)) {
-    let val = subject[property];
-    const isList = graphTypes.isList(val);
-    if(types.isArray(val) || isList) {
-      if(isList) {
-        val = val['@list'];
-      }
-      for(let i = 0; i < val.length; ++i) {
-        if(api.compareValues(value, val[i])) {
-          return true;
-        }
-      }
-    } else if(!types.isArray(value)) {
-      // avoid matching the set of values with an array value parameter
-      return api.compareValues(value, val);
-    }
+  if(!api.hasProperty(subject, property)) {
+    return false;
   }
-  return false;
+  let target = subject[property];
+  const isList = graphTypes.isList(target);
+  if(isList) {
+    target = target['@list'];
+  }
+  const isArray = types.isArray(target);
+  return _hasValue(target, isArray, value);
 };
 
 /**
@@ -245,56 +237,20 @@ api.hasValue = (subject, property, value) => {
  */
 api.addValue = (subject, property, value, options) => {
   options = options || {};
-  if(!('propertyIsArray' in options)) {
+  if(options.propertyIsArray === undefined) {
     options.propertyIsArray = false;
   }
-  if(!('valueIsArray' in options)) {
+  if(options.valueIsArray === undefined) {
     options.valueIsArray = false;
   }
-  if(!('allowDuplicate' in options)) {
+  if(options.allowDuplicate === undefined) {
     options.allowDuplicate = true;
   }
-  if(!('prependValue' in options)) {
+  if(options.prependValue === undefined) {
     options.prependValue = false;
   }
 
-  if(options.valueIsArray) {
-    subject[property] = value;
-  } else if(types.isArray(value)) {
-    if(value.length === 0 && options.propertyIsArray &&
-      !subject.hasOwnProperty(property)) {
-      subject[property] = [];
-    }
-    if(options.prependValue) {
-      value = value.concat(subject[property]);
-      subject[property] = [];
-    }
-    for(let i = 0; i < value.length; ++i) {
-      api.addValue(subject, property, value[i], options);
-    }
-  } else if(subject.hasOwnProperty(property)) {
-    // check if subject already has value if duplicates not allowed
-    const hasValue = (!options.allowDuplicate &&
-      api.hasValue(subject, property, value));
-
-    // make property an array if value not present or always an array
-    if(!types.isArray(subject[property]) &&
-      (!hasValue || options.propertyIsArray)) {
-      subject[property] = [subject[property]];
-    }
-
-    // add new value
-    if(!hasValue) {
-      if(options.prependValue) {
-        subject[property].unshift(value);
-      } else {
-        subject[property].push(value);
-      }
-    }
-  } else {
-    // add new value as set or single value
-    subject[property] = options.propertyIsArray ? [value] : value;
-  }
+  _addValue(subject, property, value, options);
 };
 
 /**
@@ -389,11 +345,10 @@ api.compareValues = (v1, v2) => {
   }
 
   // 3. equal @ids
-  if(types.isObject(v1) &&
-    ('@id' in v1) &&
-    types.isObject(v2) &&
-    ('@id' in v2)) {
-    return v1['@id'] === v2['@id'];
+  if(types.isObject(v1) && types.isObject(v2)) {
+    const id1 = v1['@id'];
+    const id2 = v2['@id'];
+    return id1 !== undefined && id1 === id2;
   }
 
   return false;
@@ -420,6 +375,131 @@ api.compareShortestLeast = (a, b) => {
   return (a < b) ? -1 : 1;
 };
 
+// internal helper for `api.addValue`
+function _addValue(subject, property, value, options) {
+  // if value is an array, assume no special checks, just set it
+  if(options.valueIsArray) {
+    subject[property] = value;
+    return;
+  }
+
+  // handle adding multiple values
+  const multipleValues = types.isArray(value);
+  if(multipleValues) {
+    // array of length `1` is handled as a single value below
+    if(value.length !== 1) {
+      return _addValues(subject, property, value, options);
+    }
+    value = value[0];
+  }
+
+  if(subject.hasOwnProperty(property)) {
+    _addToExistingProperty(subject, property, value, options);
+  } else {
+    // add new value as set or single value
+    subject[property] = options.propertyIsArray ? [value] : value;
+  }
+}
+
+// internal helper for `api.addValue`; `value.length !== 1`
+function _addValues(subject, property, value, options) {
+  // handle empty array
+  if(value.length === 0) {
+    // ensure property is set to an array
+    if(options.propertyIsArray && !subject.hasOwnProperty(property)) {
+      subject[property] = [];
+    }
+    return;
+  }
+
+  // add each element of `value` to the `target`, which may start out as
+  // `undefined` if `property` is not yet set in `subject`
+  let target = subject[property];
+  let isArray = types.isArray(target);
+  for(const nextValue of value) {
+    // if no target set yet...
+    if(target === undefined) {
+      if(options.propertyIsArray) {
+        target = [nextValue];
+        isArray = true;
+      } else {
+        target = nextValue;
+      }
+      continue;
+    }
+
+    // if duplicates not allowed, skip if `nextValue` is a dupe
+    if(!options.allowDuplicate) {
+      if(_hasValue(target, isArray, nextValue)) {
+        continue;
+      }
+    }
+
+    // add `nextValue` to target
+    if(isArray) {
+      if(options.prependValue) {
+        target.unshift(nextValue);
+      } else {
+        target.push(nextValue);
+      }
+    } else {
+      if(options.prependValue) {
+        target = [nextValue, target];
+      } else {
+        target = [target, nextValue];
+      }
+      isArray = true;
+    }
+  }
+  // ensure subject property value is updated to `target`
+  subject[property] = target;
+}
+
+// internal helper for `api.addValue`
+function _addToExistingProperty(subject, property, value, options) {
+  const target = subject[property];
+  const isArray = types.isArray(target);
+
+  // consider subject has having value if duplicates are allowed or if target
+  // has no matching value
+  const hasValue = !options.allowDuplicate &&
+    _hasValue(target, isArray, value);
+
+  if(!isArray) {
+    // make property value an array if value not present or always an array
+    if(hasValue) {
+      if(options.propertyIsArray) {
+        // value already present, just convert to an array
+        subject[property] = [target];
+      }
+    } else if(options.prependValue) {
+      subject[property] = [value, target];
+    } else {
+      subject[property] = [target, value];
+    }
+    return;
+  }
+
+  // add new value to target array if not present
+  if(!hasValue) {
+    if(options.prependValue) {
+      target.unshift(value);
+    } else {
+      target.push(value);
+    }
+  }
+}
+
+// internal helper to see if `target` has `value`; `target` can be an array
+// to look for `value` in or a simple value / undefined to compare against
+// `value`
+function _hasValue(target, isArray, value) {
+  if(isArray) {
+    return target.some(t => api.compareValues(value, t));
+  }
+  return api.compareValues(value, target);
+}
+
 /**
  * Labels the blank nodes in the given value using the given IdentifierIssuer.
  *