diff --git a/adminer/select.inc.php b/adminer/select.inc.php
index 6f51b8ff..9f6f2a98 100644
--- a/adminer/select.inc.php
+++ b/adminer/select.inc.php
@@ -544,7 +544,7 @@ if (!$columns && support("table")) {
 				echo "<fieldset>";
 				echo "<legend>" . lang('Whole result') . "</legend>";
 				$display_rows = ($exact_count ? "" : "~ ") . $found_rows;
-				$onclick = "var checked = formChecked(this, /check/); selectCount('selected', this.checked ? '$display_rows' : checked); selectCount('selected2', this.checked || !checked ? '$display_rows' : checked);";
+				$onclick = "const checked = formChecked(this, /check/); selectCount('selected', this.checked ? '$display_rows' : checked); selectCount('selected2', this.checked || !checked ? '$display_rows' : checked);";
 				echo checkbox("all", 1, 0, ($found_rows !== false ? ($exact_count ? "" : "~ ") . lang('%d row(s)', $found_rows) : ""), $onclick) . "\n";
 				echo "</fieldset>\n";
 
diff --git a/plugins/email-table.php b/plugins/email-table.php
index 57c82169..eb436a2e 100644
--- a/plugins/email-table.php
+++ b/plugins/email-table.php
@@ -34,7 +34,7 @@ class AdminerEmailTable {
 			echo "<p>" . ('Attachments') . ": <input type='file' name='email_files[]'>";
 			echo Adminer\script("qsl('input').onchange = function () {
 	this.onchange = function () { };
-	var el = this.cloneNode(true);
+	const el = this.cloneNode(true);
 	el.value = '';
 	this.parentNode.appendChild(el);
 };");
diff --git a/plugins/slugify.php b/plugins/slugify.php
index f15ab554..85a935af 100644
--- a/plugins/slugify.php
+++ b/plugins/slugify.php
@@ -35,8 +35,8 @@ class AdminerSlugify {
 			if ($slug !== null) {
 				return "<input value='" . Adminer\h($value) . "' data-maxlength='$field[length]' size='40'$attrs>"
 					. Adminer\script("qsl('input').onchange = function () {
-	var find = '$this->from';
-	var repl = '$this->to';
+	const find = '$this->from';
+	const repl = '$this->to';
 	this.form['fields[$slug]'].value = this.value.toLowerCase()
 		.replace(new RegExp('[' + find + ']', 'g'), function (str) { return repl[find.indexOf(str)]; })
 		.replace(/[^a-z0-9_]+/g, '-')
diff --git a/plugins/tables-filter.php b/plugins/tables-filter.php
index 5d353799..92e04112 100644
--- a/plugins/tables-filter.php
+++ b/plugins/tables-filter.php
@@ -13,37 +13,36 @@ class AdminerTablesFilter {
 var tablesFilterTimeout = null;
 var tablesFilterValue = '';
 
-function tablesFilter(){
-	var value = qs('#filter-field').value.toLowerCase();
+function tablesFilter() {
+	const value = qs('#filter-field').value.toLowerCase();
 	if (value == tablesFilterValue) {
 		return;
 	}
 	tablesFilterValue = value;
 	if (value != '') {
-		var reg = (value + '').replace(/([\\\.\+\*\?\[\^\]\$\(\)\{\}\=\!\<\>\|\:])/g, '\\$1');
+		const reg = (value + '').replace(/([\\\.\+\*\?\[\^\]\$\(\)\{\}\=\!\<\>\|\:])/g, '\\$1');
 		reg = new RegExp('('+ reg + ')', 'gi');
 	}
 	if (sessionStorage) {
 		sessionStorage.setItem('adminer_tables_filter', value);
 	}
-	var tables = qsa('li', qs('#tables'));
-	for (var i = 0; i < tables.length; i++) {
-		var a = null;
-		var text = tables[i].getAttribute('data-table-name');
+	for (const table of qsa('li', qs('#tables'))) {
+		let a = null;
+		let text = table.getAttribute('data-table-name');
 		if (text == null) {
-			a = qsa('a', tables[i])[1];
+			a = qsa('a', table)[1];
 			text = a.innerHTML.trim();
 
-			tables[i].setAttribute('data-table-name', text);
+			table.setAttribute('data-table-name', text);
 			a.setAttribute('data-link', 'main');
 		} else {
-			a = qs('a[data-link="main"]', tables[i]);
+			a = qs('a[data-link="main"]', table);
 		}
 		if (value == '') {
-			tables[i].className = '';
+			table.className = '';
 			a.innerHTML = text;
 		} else {
-			tables[i].className = (text.toLowerCase().indexOf(value) == -1 ? 'hidden' : '');
+			table.className = (text.toLowerCase().indexOf(value) == -1 ? 'hidden' : '');
 			a.innerHTML = text.replace(reg, '<strong>$1</strong>');
 		}
 	}
@@ -55,7 +54,7 @@ function tablesFilterInput() {
 }
 
 sessionStorage && document.addEventListener('DOMContentLoaded', function () {
-	var db = qs('#dbs').querySelector('select');
+	let db = qs('#dbs').querySelector('select');
 	db = db.options[db.selectedIndex].text;
 	if (db == sessionStorage.getItem('adminer_tables_filter_db') && sessionStorage.getItem('adminer_tables_filter')){
 		qs('#filter-field').value = sessionStorage.getItem('adminer_tables_filter');