fix String.prototype.substr feature detection and compat data

zloirock · Sep 20, 2021 · ed21ba3 · ed21ba3
1 parent 266e74d
commit ed21ba3
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Showing 6 changed files with 12 additions and 3 deletions.
diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -1,5 +1,6 @@
 ## Changelog
 ##### Unreleased
+- Fixed `String.prototype.substr` feature detection and compat data
 - Families of `.at` and `.findLast` methods marked as supported in Safari TP
 
 ##### 3.18.0 - 2021.09.20

diff --git a/packages/core-js-compat/src/data.mjs b/packages/core-js-compat/src/data.mjs
@@ -1080,7 +1080,7 @@ export const data = {
   },
   'es.string.substr': {
     chrome: '1',
-    ie: '4',
+    ie: '9',
     firefox: '1',
     opera: '4',
     safari: '1',

diff --git a/packages/core-js/modules/es.string.substr.js b/packages/core-js/modules/es.string.substr.js
@@ -8,9 +8,12 @@ var slice = ''.slice;
 var max = Math.max;
 var min = Math.min;
 
+// eslint-disable-next-line unicorn/prefer-string-slice -- required for testing
+var FORCED = !''.substr || 'ab'.substr(-1) !== 'b';
+
 // `String.prototype.substr` method
 // https://tc39.es/ecma262/#sec-string.prototype.substr
-$({ target: 'String', proto: true }, {
+$({ target: 'String', proto: true, forced: FORCED }, {
   substr: function substr(start, length) {
     var that = toString(requireObjectCoercible(this));
     var size = that.length;

diff --git a/tests/compat/tests.js b/tests/compat/tests.js
@@ -985,7 +985,8 @@ GLOBAL.tests = {
   },
   'es.string.starts-with': createIsRegExpLogicTest('startsWith'),
   'es.string.substr': function () {
-    return ''.substr;
+    // eslint-disable-next-line unicorn/prefer-string-slice -- required for testing
+    return 'ab'.substr(-1) === 'b';
   },
   'es.string.trim': createStringTrimMethodTest('trim'),
   'es.string.trim-end': [createStringTrimMethodTest('trimEnd'), function () {

diff --git a/tests/pure/es.string.substr.js b/tests/pure/es.string.substr.js
@@ -6,6 +6,8 @@ QUnit.test('String#substr', assert => {
 
   assert.same(substr('12345', 1, 3), '234');
 
+  assert.same(substr('ab', -1), 'b');
+
   /* eslint-disable es/no-symbol -- safe */
   if (typeof Symbol === 'function') {
     assert.throws(() => substr(Symbol(), 1, 3), 'throws on symbol context');

diff --git a/tests/tests/es.string.substr.js b/tests/tests/es.string.substr.js
@@ -11,6 +11,8 @@ QUnit.test('String#substr', assert => {
 
   assert.same('12345'.substr(1, 3), '234');
 
+  assert.same('ab'.substr(-1), 'b');
+
   if (typeof Symbol === 'function' && !Symbol.sham) {
     assert.throws(() => substr.call(Symbol(), 1, 3), 'throws on symbol context');
   }