diff --git a/django/contrib/admin/static/admin/js/SelectBox.js b/django/contrib/admin/static/admin/js/SelectBox.js
index 9fd93c7a8c..6716e34530 100644
--- a/django/contrib/admin/static/admin/js/SelectBox.js
+++ b/django/contrib/admin/static/admin/js/SelectBox.js
@@ -6,10 +6,7 @@
             const box = document.getElementById(id);
             SelectBox.cache[id] = [];
             const cache = SelectBox.cache[id];
-            const boxOptions = box.options;
-            const boxOptionsLength = boxOptions.length;
-            for (let i = 0, j = boxOptionsLength; i < j; i++) {
-                const node = boxOptions[i];
+            for (const node of box.options) {
                 cache.push({value: node.value, text: node.text, displayed: 1});
             }
         },
@@ -17,9 +14,7 @@
             // Repopulate HTML select box from cache
             const box = document.getElementById(id);
             box.innerHTML = '';
-            const cache = SelectBox.cache[id];
-            for (let i = 0, j = cache.length; i < j; i++) {
-                const node = cache[i];
+            for (const node of SelectBox.cache[id]) {
                 if (node.displayed) {
                     const new_option = new Option(node.text, node.value, false, false);
                     // Shows a tooltip when hovering over the option
@@ -32,14 +27,10 @@
             // Redisplay the HTML select box, displaying only the choices containing ALL
             // the words in text. (It's an AND search.)
             const tokens = text.toLowerCase().split(/\s+/);
-            const cache = SelectBox.cache[id];
-            for (let i = 0, j = cache.length; i < j; i++) {
-                const node = cache[i];
+            for (const node of SelectBox.cache[id]) {
                 node.displayed = 1;
                 const node_text = node.text.toLowerCase();
-                const numTokens = tokens.length;
-                for (let k = 0; k < numTokens; k++) {
-                    const token = tokens[k];
+                for (const token of tokens) {
                     if (node_text.indexOf(token) === -1) {
                         node.displayed = 0;
                         break; // Once the first token isn't found we're done
@@ -51,8 +42,7 @@
         delete_from_cache: function(id, value) {
             let delete_index = null;
             const cache = SelectBox.cache[id];
-            for (let i = 0, j = cache.length; i < j; i++) {
-                const node = cache[i];
+            for (const [i, node] of cache.entries()) {
                 if (node.value === value) {
                     delete_index = i;
                     break;
@@ -65,9 +55,7 @@
         },
         cache_contains: function(id, value) {
             // Check if an item is contained in the cache
-            const cache = SelectBox.cache[id];
-            for (let i = 0, j = cache.length; i < j; i++) {
-                const node = cache[i];
+            for (const node of SelectBox.cache[id]) {
                 if (node.value === value) {
                     return true;
                 }
@@ -76,10 +64,7 @@
         },
         move: function(from, to) {
             const from_box = document.getElementById(from);
-            const boxOptions = from_box.options;
-            const boxOptionsLength = boxOptions.length;
-            for (let i = 0, j = boxOptionsLength; i < j; i++) {
-                const option = boxOptions[i];
+            for (const option of from_box.options) {
                 const option_value = option.value;
                 if (option.selected && SelectBox.cache_contains(from, option_value)) {
                     SelectBox.add_to_cache(to, {value: option_value, text: option.text, displayed: 1});
@@ -91,10 +76,7 @@
         },
         move_all: function(from, to) {
             const from_box = document.getElementById(from);
-            const boxOptions = from_box.options;
-            const boxOptionsLength = boxOptions.length;
-            for (let i = 0, j = boxOptionsLength; i < j; i++) {
-                const option = boxOptions[i];
+            for (const option of from_box.options) {
                 const option_value = option.value;
                 if (SelectBox.cache_contains(from, option_value)) {
                     SelectBox.add_to_cache(to, {value: option_value, text: option.text, displayed: 1});
@@ -119,10 +101,8 @@
         },
         select_all: function(id) {
             const box = document.getElementById(id);
-            const boxOptions = box.options;
-            const boxOptionsLength = boxOptions.length;
-            for (let i = 0; i < boxOptionsLength; i++) {
-                boxOptions[i].selected = 'selected';
+            for (const option of box.options) {
+                option.selected = 'selected';
             }
         }
     };
diff --git a/django/contrib/admin/static/admin/js/SelectFilter2.js b/django/contrib/admin/static/admin/js/SelectFilter2.js
index 83ddd55a9e..6c709a08c2 100644
--- a/django/contrib/admin/static/admin/js/SelectFilter2.js
+++ b/django/contrib/admin/static/admin/js/SelectFilter2.js
@@ -16,16 +16,15 @@ Requires core.js and SelectBox.js.
             from_box.id += '_from'; // change its ID
             from_box.className = 'filtered';
 
-            const ps = from_box.parentNode.getElementsByTagName('p');
-            for (let i = 0; i < ps.length; i++) {
-                if (ps[i].classList.contains("info")) {
+            for (const p of from_box.parentNode.getElementsByTagName('p')) {
+                if (p.classList.contains("info")) {
                     // Remove <p class="info">, because it just gets in the way.
-                    from_box.parentNode.removeChild(ps[i]);
-                } else if (ps[i].classList.contains("help")) {
+                    from_box.parentNode.removeChild(p);
+                } else if (p.classList.contains("help")) {
                     // Move help text up to the top so it isn't below the select
                     // boxes or wrapped off on the side to the right of the add
                     // button:
-                    from_box.parentNode.insertBefore(ps[i], from_box.parentNode.firstChild);
+                    from_box.parentNode.insertBefore(p, from_box.parentNode.firstChild);
                 }
             }
 
diff --git a/django/contrib/admin/static/admin/js/admin/DateTimeShortcuts.js b/django/contrib/admin/static/admin/js/admin/DateTimeShortcuts.js
index 07d0d0253a..28de479763 100644
--- a/django/contrib/admin/static/admin/js/admin/DateTimeShortcuts.js
+++ b/django/contrib/admin/static/admin/js/admin/DateTimeShortcuts.js
@@ -35,9 +35,7 @@
                 DateTimeShortcuts.timezoneOffset = localOffset - serverOffset;
             }
 
-            const inputs = document.getElementsByTagName('input');
-            for (let i = 0; i < inputs.length; i++) {
-                const inp = inputs[i];
+            for (const inp of document.getElementsByTagName('input')) {
                 if (inp.type === 'text' && inp.classList.contains('vTimeField')) {
                     DateTimeShortcuts.addClock(inp);
                     DateTimeShortcuts.addTimezoneWarning(inp);
diff --git a/django/contrib/admin/static/admin/js/change_form.js b/django/contrib/admin/static/admin/js/change_form.js
index cb50120b1b..96a4c62ef4 100644
--- a/django/contrib/admin/static/admin/js/change_form.js
+++ b/django/contrib/admin/static/admin/js/change_form.js
@@ -4,8 +4,7 @@
     const modelName = document.getElementById('django-admin-form-add-constants').dataset.modelName;
     if (modelName) {
         const form = document.getElementById(modelName + '_form');
-        for (let i = 0; i < form.elements.length; i++) {
-            const element = form.elements[i];
+        for (const element of form.elements) {
             // HTMLElement.offsetParent returns null when the element is not
             // rendered.
             if (inputTags.includes(element.tagName) && !element.disabled && element.offsetParent) {
diff --git a/django/contrib/admin/static/admin/js/collapse.js b/django/contrib/admin/static/admin/js/collapse.js
index e0e2ba9f87..c6c7b0f68a 100644
--- a/django/contrib/admin/static/admin/js/collapse.js
+++ b/django/contrib/admin/static/admin/js/collapse.js
@@ -4,8 +4,7 @@
     window.addEventListener('load', function() {
         // Add anchor tag for Show/Hide link
         const fieldsets = document.querySelectorAll('fieldset.collapse');
-        for (let i = 0; i < fieldsets.length; i++) {
-            const elem = fieldsets[i];
+        for (const [i, elem] of fieldsets.entries()) {
             // Don't hide if fields in this fieldset have errors
             if (elem.querySelectorAll('div.errors, ul.errorlist').length === 0) {
                 elem.classList.add('collapsed');
@@ -37,9 +36,8 @@
                 }
             }
         };
-        const inlineDivs = document.querySelectorAll('fieldset.module');
-        for (let i = 0; i < inlineDivs.length; i++) {
-            inlineDivs[i].addEventListener('click', toggleFunc);
-        }
+        document.querySelectorAll('fieldset.module').forEach(function(el) {
+            el.addEventListener('click', toggleFunc);
+        });
     });
 }
diff --git a/django/contrib/admin/static/admin/js/collapse.min.js b/django/contrib/admin/static/admin/js/collapse.min.js
index cd78b6984c..06201c597f 100644
--- a/django/contrib/admin/static/admin/js/collapse.min.js
+++ b/django/contrib/admin/static/admin/js/collapse.min.js
@@ -1,2 +1,2 @@
-'use strict';window.addEventListener("load",function(){var d=document.querySelectorAll("fieldset.collapse");for(var c=0;c<d.length;c++){var a=d[c];if(0===a.querySelectorAll("div.errors, ul.errorlist").length){a.classList.add("collapsed");a=a.querySelector("h2");const b=document.createElement("a");b.id="fieldsetcollapser"+c;b.className="collapse-toggle";b.href="#";b.textContent=gettext("Show");a.appendChild(document.createTextNode(" ("));a.appendChild(b);a.appendChild(document.createTextNode(")"))}}d=
-function(b){if(b.target.matches(".collapse-toggle")){b.preventDefault();b.stopPropagation();const a=b.target.closest("fieldset");a.classList.contains("collapsed")?(b.target.textContent=gettext("Hide"),a.classList.remove("collapsed")):(b.target.textContent=gettext("Show"),a.classList.add("collapsed"))}};c=document.querySelectorAll("fieldset.module");for(a=0;a<c.length;a++)c[a].addEventListener("click",d)});
+'use strict';window.addEventListener("load",function(){var c=document.querySelectorAll("fieldset.collapse");for(const [a,b]of c.entries())if(0===b.querySelectorAll("div.errors, ul.errorlist").length){b.classList.add("collapsed");c=b.querySelector("h2");const d=document.createElement("a");d.id="fieldsetcollapser"+a;d.className="collapse-toggle";d.href="#";d.textContent=gettext("Show");c.appendChild(document.createTextNode(" ("));c.appendChild(d);c.appendChild(document.createTextNode(")"))}const e=
+function(a){if(a.target.matches(".collapse-toggle")){a.preventDefault();a.stopPropagation();const b=a.target.closest("fieldset");b.classList.contains("collapsed")?(a.target.textContent=gettext("Hide"),b.classList.remove("collapsed")):(a.target.textContent=gettext("Show"),b.classList.add("collapsed"))}};document.querySelectorAll("fieldset.module").forEach(function(a){a.addEventListener("click",e)})});
diff --git a/django/contrib/admin/static/admin/js/urlify.js b/django/contrib/admin/static/admin/js/urlify.js
index b9031cde87..7faa65912c 100644
--- a/django/contrib/admin/static/admin/js/urlify.js
+++ b/django/contrib/admin/static/admin/js/urlify.js
@@ -131,20 +131,10 @@
                 return;
             }
             Downcoder.map = {};
-            Downcoder.chars = [];
-            for (let i = 0; i < ALL_DOWNCODE_MAPS.length; i++) {
-                const lookup = ALL_DOWNCODE_MAPS[i];
-                for (const c in lookup) {
-                    if (lookup.hasOwnProperty(c)) {
-                        Downcoder.map[c] = lookup[c];
-                    }
-                }
-            }
-            for (const k in Downcoder.map) {
-                if (Downcoder.map.hasOwnProperty(k)) {
-                    Downcoder.chars.push(k);
-                }
+            for (const lookup of ALL_DOWNCODE_MAPS) {
+                Object.assign(Downcoder.map, lookup);
             }
+            Downcoder.chars = Object.keys(Downcoder.map);
             Downcoder.regex = new RegExp(Downcoder.chars.join('|'), 'g');
         }
     };