diff --git a/lib/assert.js b/lib/assert.js
index 6a11e93..6ed635a 100755
--- a/lib/assert.js
+++ b/lib/assert.js
@@ -2,6 +2,7 @@
 
 const AssertError = require('./error');
 
+
 const internals = {};
 
 
diff --git a/lib/escapeHtml.js b/lib/escapeHtml.js
index ddef2b6..c2dd443 100755
--- a/lib/escapeHtml.js
+++ b/lib/escapeHtml.js
@@ -29,8 +29,8 @@ module.exports = function (input) {
 
 internals.escapeHtmlChar = function (charCode) {
 
-    const namedEscape = internals.namedHtml[charCode];
-    if (typeof namedEscape !== 'undefined') {
+    const namedEscape = internals.namedHtml.get(charCode);
+    if (namedEscape) {
         return namedEscape;
     }
 
@@ -45,27 +45,27 @@ internals.escapeHtmlChar = function (charCode) {
 
 internals.isSafe = function (charCode) {
 
-    return (typeof internals.safeCharCodes[charCode] !== 'undefined');
+    return internals.safeCharCodes.has(charCode);
 };
 
 
-internals.namedHtml = {
-    '38': '&',
-    '60': '<',
-    '62': '>',
-    '34': '"',
-    '160': ' ',
-    '162': '¢',
-    '163': '£',
-    '164': '¤',
-    '169': '©',
-    '174': '®'
-};
+internals.namedHtml = new Map([
+    [38, '&'],
+    [60, '<'],
+    [62, '>'],
+    [34, '"'],
+    [160, ' '],
+    [162, '¢'],
+    [163, '£'],
+    [164, '¤'],
+    [169, '©'],
+    [174, '®']
+]);
 
 
 internals.safeCharCodes = (function () {
 
-    const safe = {};
+    const safe = new Set();
 
     for (let i = 32; i < 123; ++i) {
 
@@ -79,7 +79,7 @@ internals.safeCharCodes = (function () {
             i === 58 ||                     // :
             i === 95) {                     // _
 
-            safe[i] = null;
+            safe.add(i);
         }
     }
 
diff --git a/lib/escapeJson.js b/lib/escapeJson.js
index e6e94b3..243edfb 100755
--- a/lib/escapeJson.js
+++ b/lib/escapeJson.js
@@ -9,33 +9,20 @@ module.exports = function (input) {
         return '';
     }
 
-    const lessThan = 0x3C;
-    const greaterThan = 0x3E;
-    const andSymbol = 0x26;
-    const lineSeperator = 0x2028;
-
-    // replace method
-    let charCode;
-    return input.replace(/[<>&\u2028\u2029]/g, (match) => {
-
-        charCode = match.charCodeAt(0);
+    return input.replace(/[<>&\u2028\u2029]/g, internals.escape);
+};
 
-        if (charCode === lessThan) {
-            return '\\u003c';
-        }
 
-        if (charCode === greaterThan) {
-            return '\\u003e';
-        }
+internals.escape = function (char) {
 
-        if (charCode === andSymbol) {
-            return '\\u0026';
-        }
+    return internals.replacements.get(char);
+};
 
-        if (charCode === lineSeperator) {
-            return '\\u2028';
-        }
 
-        return '\\u2029';
-    });
-};
+internals.replacements = new Map([
+    ['<', '\\u003c'],
+    ['>', '\\u003e'],
+    ['&', '\\u0026'],
+    ['\u2028', '\\u2028'],
+    ['\u2029', '\\u2029']
+]);
diff --git a/lib/flatten.js b/lib/flatten.js
index 726e231..a5ea622 100755
--- a/lib/flatten.js
+++ b/lib/flatten.js
@@ -7,12 +7,12 @@ module.exports = internals.flatten = function (array, target) {
 
     const result = target || [];
 
-    for (let i = 0; i < array.length; ++i) {
-        if (Array.isArray(array[i])) {
-            internals.flatten(array[i], result);
+    for (const entry of array) {
+        if (Array.isArray(entry)) {
+            internals.flatten(entry, result);
         }
         else {
-            result.push(array[i]);
+            result.push(entry);
         }
     }
 
diff --git a/lib/once.js b/lib/once.js
index de94ea0..c825767 100755
--- a/lib/once.js
+++ b/lib/once.js
@@ -1,16 +1,18 @@
 'use strict';
 
-const internals = {};
+const internals = {
+    wrapped: Symbol('wrapped')
+};
 
 
 module.exports = function (method) {
 
-    if (method._hoekOnce) {
+    if (method[internals.wrapped]) {
         return method;
     }
 
     let once = false;
-    const wrapped = function (...args) {
+    const wrappedFn = function (...args) {
 
         if (!once) {
             once = true;
@@ -18,6 +20,6 @@ module.exports = function (method) {
         }
     };
 
-    wrapped._hoekOnce = true;
-    return wrapped;
+    wrappedFn[internals.wrapped] = true;
+    return wrappedFn;
 };
diff --git a/lib/reach.js b/lib/reach.js
index 3791b37..53b7c24 100755
--- a/lib/reach.js
+++ b/lib/reach.js
@@ -22,7 +22,7 @@ module.exports = function (obj, chain, options) {
 
     const isChainArray = Array.isArray(chain);
 
-    Assert(!isChainArray || !options.separator, 'Separator option no valid for array-based chain');
+    Assert(!isChainArray || !options.separator, 'Separator option is not valid for array-based chain');
 
     const path = isChainArray ? chain : chain.split(options.separator || '.');
     let ref = obj;
diff --git a/lib/stringify.js b/lib/stringify.js
index 88d0fc4..82152cf 100755
--- a/lib/stringify.js
+++ b/lib/stringify.js
@@ -6,7 +6,7 @@ const internals = {};
 module.exports = function (...args) {
 
     try {
-        return JSON.stringify.apply(null, args);
+        return JSON.stringify(...args);
     }
     catch (err) {
         return '[Cannot display object: ' + err.message + ']';
diff --git a/test/index.js b/test/index.js
index 9e9747f..f5db161 100755
--- a/test/index.js
+++ b/test/index.js
@@ -2141,7 +2141,7 @@ describe('assert()', () => {
 
         expect(() => {
 
-            Hoek.assert(false, 'This', 'is', new Error('spinal'), new Error('tap'));
+            Hoek.assert(false, new Error('This'), 'is', 'spinal', new Error('tap'));
         }).to.throw('This is spinal tap');
     });