Shim String.repeat

Author: lukechilds

internal/assert/assertion_error.js

@@ -16,6 +16,44 @@ function endsWith(str, search, this_len) {
 	return str.substring(this_len - search.length, this_len) === search;
 }
 
+// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/repeat
+function repeat(str, count) {
+  if (str == null)
+    throw new TypeError('can\'t convert ' + this + ' to object');
+
+  str = '' + str;
+  // To convert string to integer.
+  count = +count;
+  // Check NaN
+  if (count != count)
+    count = 0;
+
+  if (count < 0)
+    throw new RangeError('repeat count must be non-negative');
+
+  if (count == Infinity)
+    throw new RangeError('repeat count must be less than infinity');
+
+  count = Math.floor(count);
+  if (str.length == 0 || count == 0)
+    return '';
+
+  // Ensuring count is a 31-bit integer allows us to heavily optimize the
+  // main part. But anyway, most current (August 2014) browsers can't handle
+  // strings 1 << 28 chars or longer, so:
+  if (str.length * count >= 1 << 28)
+    throw new RangeError('repeat count must not overflow maximum string size');
+
+  var maxCount = str.length * count;
+  count = Math.floor(Math.log(count) / Math.log(2));
+  while (count) {
+     str += str;
+     count--;
+  }
+  str += str.substring(0, maxCount - str.length);
+  return str;
+}
+
 let blue = '';
 let green = '';
 let red = '';
@@ -128,7 +166,7 @@ function createErrDiff(actual, expected, operator) {
         if (i > 2) {
           // Add position indicator for the first mismatch in case it is a
           // single line and the input length is less than the column length.
-          indicator = `\n  ${' '.repeat(i)}^`;
+          indicator = `\n  ${repeat(' ', i)}^`;
           i = 0;
         }
       }

test/common/index.js

@@ -4,6 +4,44 @@ const getOwnPropertyDescriptors = Object.getOwnPropertyDescriptors
   ? Object.getOwnPropertyDescriptors
   : require('object.getownpropertydescriptors');
 
+// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/repeat
+function repeat(str, count) {
+  if (str == null)
+    throw new TypeError('can\'t convert ' + this + ' to object');
+
+  str = '' + str;
+  // To convert string to integer.
+  count = +count;
+  // Check NaN
+  if (count != count)
+    count = 0;
+
+  if (count < 0)
+    throw new RangeError('repeat count must be non-negative');
+
+  if (count == Infinity)
+    throw new RangeError('repeat count must be less than infinity');
+
+  count = Math.floor(count);
+  if (str.length == 0 || count == 0)
+    return '';
+
+  // Ensuring count is a 31-bit integer allows us to heavily optimize the
+  // main part. But anyway, most current (August 2014) browsers can't handle
+  // strings 1 << 28 chars or longer, so:
+  if (str.length * count >= 1 << 28)
+    throw new RangeError('repeat count must not overflow maximum string size');
+
+  var maxCount = str.length * count;
+  count = Math.floor(Math.log(count) / Math.log(2));
+  while (count) {
+     str += str;
+     count--;
+  }
+  str += str.substring(0, maxCount - str.length);
+  return str;
+}
+
 const isBrowser = typeof window !== 'undefined';
 
 const bigIntSupported = typeof BigInt !== 'undefined';
@@ -234,6 +272,7 @@ process.on('unhandledRejection', crashOnUnhandledRejection);
 
 module.exports = {
   getOwnPropertyDescriptors,
+  repeat,
   isBrowser,
   bigIntSupported,
   symbolToStringTagSupported,

test/parallel/test-assert-deep.js

@@ -676,7 +676,7 @@ assert.throws(
 );
 
 assert.throws(
-  () => { assert.notDeepEqual('a'.repeat(1024), 'a'.repeat(1024)); },
+  () => { assert.notDeepEqual(common.repeat('a', 1024), common.repeat('a', 1024)); },
   AssertionError,
   'notDeepEqual("a".repeat(1024), "a".repeat(1024))'
 );

test/parallel/test-assert.js

@@ -82,7 +82,7 @@ assert.throws(
 );
 
 assert.throws(
-  () => a.notStrictEqual('a '.repeat(30), 'a '.repeat(30)),
+  () => a.notStrictEqual(common.repeat('a ', 30), common.repeat('a ', 30)),
   {
     // message: 'Expected "actual" to be strictly unequal to: ' +
     //          `'${'a '.repeat(30)}'`,
@@ -393,7 +393,7 @@ assert.throws(() => { throw new Error(); }, (err) => err instanceof Error);
 
 // Long values should be truncated for display.
 assert.throws(() => {
-  assert.strictEqual('A'.repeat(1000), '');
+  assert.strictEqual(common.repeat('A', 1000), '');
 }, {
   code: 'ERR_ASSERTION',
   // message: `${strictEqualMessageStart}+ actual - expected\n\n` +
@@ -595,9 +595,9 @@ assert.throws(
     `${actExp} ... Lines skipped\n` +
     '\n' +
     '  [\n' +
-    '+   1,\n'.repeat(10) +
+    common.repeat('+   1,\n', 10) +
     '...\n' +
-    '-   2,\n'.repeat(10) +
+    common.repeat('-   2,\n', 10) +
     '...';
   assert.throws(
     () => assert.deepEqual(Array(12).fill(1), Array(12).fill(2)),
@@ -632,7 +632,7 @@ assert.throws(
   );
 
   message = 'Expected "actual" not to be strictly deep-equal to:' +
-            `\n\n[${'\n  1,'.repeat(25)}\n...\n`;
+            `\n\n[${common.repeat('\n  1,', 25)}\n...\n`;
   const data = Array(31).fill(1);
   assert.throws(
     () => assert.notDeepEqual(data, data),