diff --git a/src/librustdoc/html/static/js/main.js b/src/librustdoc/html/static/js/main.js
index 70dbfd4442540..ad96b6b052da9 100644
--- a/src/librustdoc/html/static/js/main.js
+++ b/src/librustdoc/html/static/js/main.js
@@ -4,40 +4,6 @@
"use strict";
-if (!String.prototype.startsWith) {
- String.prototype.startsWith = function(searchString, position) {
- position = position || 0;
- return this.indexOf(searchString, position) === position;
- };
-}
-if (!String.prototype.endsWith) {
- String.prototype.endsWith = function(suffix, length) {
- const l = length || this.length;
- return this.indexOf(suffix, l - suffix.length) !== -1;
- };
-}
-
-if (!DOMTokenList.prototype.add) {
- DOMTokenList.prototype.add = function(className) {
- if (className && !hasClass(this, className)) {
- if (this.className && this.className.length > 0) {
- this.className += " " + className;
- } else {
- this.className = className;
- }
- }
- };
-}
-
-if (!DOMTokenList.prototype.remove) {
- DOMTokenList.prototype.remove = function(className) {
- if (className && this.className) {
- this.className = (" " + this.className + " ").replace(" " + className + " ", " ")
- .trim();
- }
- };
-}
-
// Get a value from the rustdoc-vars div, which is used to convey data from
// Rust to the JS. If there is no such element, return null.
function getVar(name) {