diff --git a/benchmark/index.js b/benchmark/index.js
index 43ced8a..ecf99b5 100644
--- a/benchmark/index.js
+++ b/benchmark/index.js
@@ -11,96 +11,96 @@ const plainObjectClone = require('plain-object-clone')
 const nanoCopy = require('nano-copy')
 const ramdaClone = require('ramda').clone
 const cloneDefaults = clone()
-const cloneProto = clone({proto: true})
-const cloneCircles = clone({circles: true})
-const cloneCirclesProto = clone({circles: true, proto: true})
+const cloneProto = clone({ proto: true })
+const cloneCircles = clone({ circles: true })
+const cloneCirclesProto = clone({ circles: true, proto: true })
 const max = 1000
 
-var run = bench([
+const run = bench([
   function benchDeepCopy (cb) {
-    for (var i = 0; i < max; i++) {
+    for (let i = 0; i < max; i++) {
       deepCopy(obj)
     }
     setImmediate(cb)
   },
   function benchLodashCloneDeep (cb) {
-    for (var i = 0; i < max; i++) {
+    for (let i = 0; i < max; i++) {
       lodashCloneDeep(obj)
     }
     setImmediate(cb)
   },
   function benchCloneDeep (cb) {
-    for (var i = 0; i < max; i++) {
+    for (let i = 0; i < max; i++) {
       cloneDeep(obj)
     }
     setImmediate(cb)
   },
   function benchFastCopy (cb) {
-    for (var i = 0; i < max; i++) {
+    for (let i = 0; i < max; i++) {
       fastCopy(obj)
     }
     setImmediate(cb)
   },
   function benchFastestJsonCopy (cb) {
-    for (var i = 0; i < max; i++) {
+    for (let i = 0; i < max; i++) {
       copyFastestJsonCopy(obj)
     }
     setImmediate(cb)
   },
   function benchPlainObjectClone (cb) {
-    for (var i = 0; i < max; i++) {
+    for (let i = 0; i < max; i++) {
       plainObjectClone(obj)
     }
     setImmediate(cb)
   },
   function benchNanoCopy (cb) {
-    for (var i = 0; i < max; i++) {
+    for (let i = 0; i < max; i++) {
       nanoCopy(obj)
     }
     setImmediate(cb)
   },
   function benchRamdaClone (cb) {
-    for (var i = 0; i < max; i++) {
+    for (let i = 0; i < max; i++) {
       ramdaClone(obj)
     }
     setImmediate(cb)
   },
   function benchJsonParseJsonStringify (cb) {
-    for (var i = 0; i < max; i++) {
+    for (let i = 0; i < max; i++) {
       JSON.parse(JSON.stringify(obj))
     }
     setImmediate(cb)
   },
   function benchRfdc (cb) {
-    for (var i = 0; i < max; i++) {
+    for (let i = 0; i < max; i++) {
       cloneDefaults(obj)
     }
     setImmediate(cb)
   },
   function benchRfdcProto (cb) {
-    for (var i = 0; i < max; i++) {
+    for (let i = 0; i < max; i++) {
       cloneProto(obj)
     }
     setImmediate(cb)
   },
   function benchRfdcCircles (cb) {
-    for (var i = 0; i < max; i++) {
+    for (let i = 0; i < max; i++) {
       cloneCircles(obj)
     }
     setImmediate(cb)
   },
   function benchRfdcCirclesProto (cb) {
-    for (var i = 0; i < max; i++) {
+    for (let i = 0; i < max; i++) {
       cloneCirclesProto(obj)
     }
     setImmediate(cb)
   },
   function benchStructuredClone (cb) {
-    for (var i = 0; i < max; i++) {
+    for (let i = 0; i < max; i++) {
       structuredClone(obj)
     }
     setImmediate(cb)
-  },
+  }
 ], 100)
 
 run(run)
diff --git a/benchmark/shallow.js b/benchmark/shallow.js
index 7d5b802..0d70bcf 100644
--- a/benchmark/shallow.js
+++ b/benchmark/shallow.js
@@ -4,99 +4,99 @@ const deepCopy = require('deep-copy')
 const lodashCloneDeep = require('lodash.clonedeep')
 const cloneDeep = require('clone-deep')
 const fastCopy = require('fast-copy').default
-const obj = {a: 'a', b: 'b', c: 'c'}
+const obj = { a: 'a', b: 'b', c: 'c' }
 const clone = require('..')
 const copyFastestJsonCopy = require('fastest-json-copy').copy
 const plainObjectClone = require('plain-object-clone')
 const nanoCopy = require('nano-copy')
 const ramdaClone = require('ramda').clone
 const cloneDefaults = clone()
-const cloneProto = clone({proto: true})
-const cloneCircles = clone({circles: true})
-const cloneCirclesProto = clone({circles: true, proto: true})
+const cloneProto = clone({ proto: true })
+const cloneCircles = clone({ circles: true })
+const cloneCirclesProto = clone({ circles: true, proto: true })
 const max = 1000
 /* eslint no-unused-vars: ["error", { "varsIgnorePattern": "^x$" }] */
-var run = bench([
+const run = bench([
   function benchDeepCopy (cb) {
-    for (var i = 0; i < max; i++) {
+    for (let i = 0; i < max; i++) {
       deepCopy(obj)
     }
     setImmediate(cb)
   },
   function benchLodashCloneDeep (cb) {
-    for (var i = 0; i < max; i++) {
+    for (let i = 0; i < max; i++) {
       lodashCloneDeep(obj)
     }
     setImmediate(cb)
   },
   function benchCloneDeep (cb) {
-    for (var i = 0; i < max; i++) {
+    for (let i = 0; i < max; i++) {
       cloneDeep(obj)
     }
     setImmediate(cb)
   },
   function benchFastCopy (cb) {
-    for (var i = 0; i < max; i++) {
+    for (let i = 0; i < max; i++) {
       fastCopy(obj)
     }
     setImmediate(cb)
   },
   function benchFastestJsonCopy (cb) {
-    for (var i = 0; i < max; i++) {
+    for (let i = 0; i < max; i++) {
       copyFastestJsonCopy(obj)
     }
     setImmediate(cb)
   },
   function benchPlainObjectClone (cb) {
-    for (var i = 0; i < max; i++) {
+    for (let i = 0; i < max; i++) {
       plainObjectClone(obj)
     }
     setImmediate(cb)
   },
   function benchNanoCopy (cb) {
-    for (var i = 0; i < max; i++) {
+    for (let i = 0; i < max; i++) {
       nanoCopy(obj)
     }
     setImmediate(cb)
   },
   function benchRamdaClone (cb) {
-    for (var i = 0; i < max; i++) {
+    for (let i = 0; i < max; i++) {
       ramdaClone(obj)
     }
     setImmediate(cb)
   },
   function benchObjectAssign (cb) {
-    for (var i = 0; i < max; i++) {
-      var x = Object.assign({}, obj)
+    for (let i = 0; i < max; i++) {
+      const x = Object.assign({}, obj)
     }
     setImmediate(cb)
   },
   function benchObjectSpread (cb) {
-    for (var i = 0; i < max; i++) {
-      var x = {...obj}
+    for (let i = 0; i < max; i++) {
+      const x = { ...obj }
     }
     setImmediate(cb)
   },
   function benchRfdc (cb) {
-    for (var i = 0; i < max; i++) {
+    for (let i = 0; i < max; i++) {
       cloneDefaults(obj)
     }
     setImmediate(cb)
   },
   function benchRfdcProto (cb) {
-    for (var i = 0; i < max; i++) {
+    for (let i = 0; i < max; i++) {
       cloneProto(obj)
     }
     setImmediate(cb)
   },
   function benchRfdcCircles (cb) {
-    for (var i = 0; i < max; i++) {
+    for (let i = 0; i < max; i++) {
       cloneCircles(obj)
     }
     setImmediate(cb)
   },
   function benchRfdcCirclesProto (cb) {
-    for (var i = 0; i < max; i++) {
+    for (let i = 0; i < max; i++) {
       cloneCirclesProto(obj)
     }
     setImmediate(cb)
diff --git a/index.js b/index.js
index 3b438a4..41a49c1 100644
--- a/index.js
+++ b/index.js
@@ -16,11 +16,11 @@ function rfdc (opts) {
   return opts.proto ? cloneProto : clone
 
   function cloneArray (a, fn) {
-    var keys = Object.keys(a)
-    var a2 = new Array(keys.length)
-    for (var i = 0; i < keys.length; i++) {
-      var k = keys[i]
-      var cur = a[k]
+    const keys = Object.keys(a)
+    const a2 = new Array(keys.length)
+    for (let i = 0; i < keys.length; i++) {
+      const k = keys[i]
+      const cur = a[k]
       if (typeof cur !== 'object' || cur === null) {
         a2[k] = cur
       } else if (cur instanceof Date) {
@@ -40,10 +40,10 @@ function rfdc (opts) {
     if (Array.isArray(o)) return cloneArray(o, clone)
     if (o instanceof Map) return new Map(cloneArray(Array.from(o), clone))
     if (o instanceof Set) return new Set(cloneArray(Array.from(o), clone))
-    var o2 = {}
-    for (var k in o) {
+    const o2 = {}
+    for (const k in o) {
       if (Object.hasOwnProperty.call(o, k) === false) continue
-      var cur = o[k]
+      const cur = o[k]
       if (typeof cur !== 'object' || cur === null) {
         o2[k] = cur
       } else if (cur instanceof Date) {
@@ -67,9 +67,9 @@ function rfdc (opts) {
     if (Array.isArray(o)) return cloneArray(o, cloneProto)
     if (o instanceof Map) return new Map(cloneArray(Array.from(o), cloneProto))
     if (o instanceof Set) return new Set(cloneArray(Array.from(o), cloneProto))
-    var o2 = {}
-    for (var k in o) {
-      var cur = o[k]
+    const o2 = {}
+    for (const k in o) {
+      const cur = o[k]
       if (typeof cur !== 'object' || cur === null) {
         o2[k] = cur
       } else if (cur instanceof Date) {
@@ -89,17 +89,17 @@ function rfdc (opts) {
 }
 
 function rfdcCircles (opts) {
-  var refs = []
-  var refsNew = []
+  const refs = []
+  const refsNew = []
 
   return opts.proto ? cloneProto : clone
 
   function cloneArray (a, fn) {
-    var keys = Object.keys(a)
-    var a2 = new Array(keys.length)
-    for (var i = 0; i < keys.length; i++) {
-      var k = keys[i]
-      var cur = a[k]
+    const keys = Object.keys(a)
+    const a2 = new Array(keys.length)
+    for (let i = 0; i < keys.length; i++) {
+      const k = keys[i]
+      const cur = a[k]
       if (typeof cur !== 'object' || cur === null) {
         a2[k] = cur
       } else if (cur instanceof Date) {
@@ -107,7 +107,7 @@ function rfdcCircles (opts) {
       } else if (ArrayBuffer.isView(cur)) {
         a2[k] = copyBuffer(cur)
       } else {
-        var index = refs.indexOf(cur)
+        const index = refs.indexOf(cur)
         if (index !== -1) {
           a2[k] = refsNew[index]
         } else {
@@ -124,12 +124,12 @@ function rfdcCircles (opts) {
     if (Array.isArray(o)) return cloneArray(o, clone)
     if (o instanceof Map) return new Map(cloneArray(Array.from(o), clone))
     if (o instanceof Set) return new Set(cloneArray(Array.from(o), clone))
-    var o2 = {}
+    const o2 = {}
     refs.push(o)
     refsNew.push(o2)
-    for (var k in o) {
+    for (const k in o) {
       if (Object.hasOwnProperty.call(o, k) === false) continue
-      var cur = o[k]
+      const cur = o[k]
       if (typeof cur !== 'object' || cur === null) {
         o2[k] = cur
       } else if (cur instanceof Date) {
@@ -141,7 +141,7 @@ function rfdcCircles (opts) {
       } else if (ArrayBuffer.isView(cur)) {
         o2[k] = copyBuffer(cur)
       } else {
-        var i = refs.indexOf(cur)
+        const i = refs.indexOf(cur)
         if (i !== -1) {
           o2[k] = refsNew[i]
         } else {
@@ -160,11 +160,11 @@ function rfdcCircles (opts) {
     if (Array.isArray(o)) return cloneArray(o, cloneProto)
     if (o instanceof Map) return new Map(cloneArray(Array.from(o), cloneProto))
     if (o instanceof Set) return new Set(cloneArray(Array.from(o), cloneProto))
-    var o2 = {}
+    const o2 = {}
     refs.push(o)
     refsNew.push(o2)
-    for (var k in o) {
-      var cur = o[k]
+    for (const k in o) {
+      const cur = o[k]
       if (typeof cur !== 'object' || cur === null) {
         o2[k] = cur
       } else if (cur instanceof Date) {
@@ -176,7 +176,7 @@ function rfdcCircles (opts) {
       } else if (ArrayBuffer.isView(cur)) {
         o2[k] = copyBuffer(cur)
       } else {
-        var i = refs.indexOf(cur)
+        const i = refs.indexOf(cur)
         if (i !== -1) {
           o2[k] = refsNew[i]
         } else {
diff --git a/package.json b/package.json
index d9edae1..1050e94 100644
--- a/package.json
+++ b/package.json
@@ -54,7 +54,7 @@
     "nano-copy": "^0.1.0",
     "plain-object-clone": "^1.1.0",
     "ramda": "^0.27.1",
-    "standard": "^11.0.1",
+    "standard": "^17.0.0",
     "tap": "^12.0.1",
     "tsd": "^0.7.4"
   },
diff --git a/test/index.js b/test/index.js
index 458712f..a8e3cf4 100644
--- a/test/index.js
+++ b/test/index.js
@@ -223,7 +223,7 @@ function types (clone, label) {
   })
   test(`${label} copies TypedArrays from object correctly`, async ({ ok, is, isNot }) => {
     const [input1, input2] = [rnd(10), rnd(10)]
-    var buffer = new ArrayBuffer(8)
+    const buffer = new ArrayBuffer(8)
     const int32View = new Int32Array(buffer)
     int32View[0] = input1
     int32View[1] = input2
@@ -235,7 +235,7 @@ function types (clone, label) {
   })
   test(`${label} copies TypedArrays from array correctly`, async ({ ok, is, isNot }) => {
     const [input1, input2] = [rnd(10), rnd(10)]
-    var buffer = new ArrayBuffer(16)
+    const buffer = new ArrayBuffer(16)
     const int32View = new Int32Array(buffer)
     int32View[0] = input1
     int32View[1] = input2
@@ -247,7 +247,7 @@ function types (clone, label) {
   })
   test(`${label} copies complex TypedArrays`, async ({ ok, deepEqual, is, isNot }) => {
     const [input1, input2, input3] = [rnd(10), rnd(10), rnd(10)]
-    var buffer = new ArrayBuffer(4)
+    const buffer = new ArrayBuffer(4)
     const view1 = new Int8Array(buffer, 0, 2)
     const view2 = new Int8Array(buffer, 2, 2)
     const view3 = new Int8Array(buffer)