diff --git a/src/js.rs b/src/js.rs
index 2cdc6ce4..614efe6d 100644
--- a/src/js.rs
+++ b/src/js.rs
@@ -376,6 +376,13 @@ extern {
     /// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/substring
     #[wasm_bindgen(method, js_class = "String")]
     pub fn substring(this: &JsString, index_start: u32, index_end: u32) -> JsString;
+
+    /// The substr() method returns the part of a string between
+    /// the start index and a number of characters after it.
+    ///
+    /// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/substr
+    #[wasm_bindgen(method, js_class = "String")]
+    pub fn substr(this: &JsString, start: i32, length: i32) -> JsString;
 }
 
 impl<'a> From<&'a str> for JsString {
diff --git a/tests/all/js_globals/JsString.rs b/tests/all/js_globals/JsString.rs
index cc2852d5..9bfe0ba4 100644
--- a/tests/all/js_globals/JsString.rs
+++ b/tests/all/js_globals/JsString.rs
@@ -31,35 +31,6 @@ fn char_at() {
         .test()
 }
 
-#[test]
-fn slice() {
-    project()
-        .file("src/lib.rs", r#"
-            #![feature(proc_macro, wasm_custom_section)]
-
-            extern crate wasm_bindgen;
-            use wasm_bindgen::prelude::*;
-            use wasm_bindgen::js;
-
-            #[wasm_bindgen]
-            pub fn create_slice(this: &js::JsString, start: u32, end: u32) -> js::JsString {
-                this.slice(start, end)
-            }
-        "#)
-        .file("test.ts", r#"
-            import * as assert from "assert";
-            import * as wasm from "./out";
-
-            export function test() {
-                let characters = "acxn18";
-                let subset = wasm.create_slice(characters, 1, 3);
-
-                assert.equal(subset, "cx");
-            }
-        "#)
-        .test()
-}
-
 #[test]
 fn starts_with() {
     project()
@@ -168,3 +139,68 @@ fn index_of() {
         "#)
         .test()
 }
+
+#[test]
+fn slice() {
+    project()
+        .file("src/lib.rs", r#"
+            #![feature(proc_macro, wasm_custom_section)]
+
+            extern crate wasm_bindgen;
+            use wasm_bindgen::prelude::*;
+            use wasm_bindgen::js;
+
+            #[wasm_bindgen]
+            pub fn create_slice(this: &js::JsString, start: u32, end: u32) -> js::JsString {
+                this.slice(start, end)
+            }
+        "#)
+        .file("test.ts", r#"
+            import * as assert from "assert";
+            import * as wasm from "./out";
+
+            export function test() {
+                let characters = "acxn18";
+                let subset = wasm.create_slice(characters, 1, 3);
+
+                assert.equal(subset, "cx");
+            }
+        "#)
+        .test()
+}
+
+#[test]
+fn substr() {
+    project()
+        .file("src/lib.rs", r#"
+            #![feature(proc_macro, wasm_custom_section)]
+
+            extern crate wasm_bindgen;
+            use wasm_bindgen::prelude::*;
+            use wasm_bindgen::js;
+
+            #[wasm_bindgen]
+            pub fn create_substr(this: &js::JsString, start: i32, length: i32) -> js::JsString {
+                this.substr(start, length)
+            }
+        "#)
+        .file("test.ts", r#"
+            import * as assert from "assert";
+            import * as wasm from "./out";
+
+            export function test() {
+                let aString = "Mozilla";
+
+                assert.equal(wasm.create_substr(aString, 0, 1), "M");
+                assert.equal(wasm.create_substr(aString, 1, 0), "");
+                assert.equal(wasm.create_substr(aString, -1, 1), "a");
+                assert.equal(wasm.create_substr(aString, 1, -1), "");
+                // TODO: Uncomment and test these assertions, once we have support for optional parameters
+                // assert.equal(wasm.create_substr(aString, -3), "lla");
+                // assert.equal(wasm.create_substr(aString, 1), "ozilla");
+                assert.equal(wasm.create_substr(aString, -20, 2), "Mo");
+                assert.equal(wasm.create_substr(aString, 20, 2), "");
+            }
+        "#)
+        .test()
+}