testcase for an 'string repeat' idiom

ecmascript-testcases/test-dev-array-rep-trick.js

@@ -0,0 +1,37 @@
+/*===
+10 x
+10 y
+100000 x
+100000 y
+===*/
+
+/* String repeat can be implemented with an array join. */
+
+function dump(x) {
+    var ch = '?'
+    if (x.length > 0) {
+        ch = x.charAt(0);
+        for (var i = 0; i < x.length; i++) {
+            if (x.charAt(i) !== ch) {
+                throw new Error('error in string');
+            }
+        }
+    }
+    print(x.length, ch);
+}
+
+try {
+    dump(Array.prototype.join.call({ length: 10 + 1 }, 'x'));
+    var arr = []; arr.length = 10 + 1;
+    dump(arr.join('y'));
+} catch (e) {
+    print(e);
+}
+
+try {
+    dump(Array.prototype.join.call({ length: 100000 + 1 }, 'x'));
+    var arr = []; arr.length = 100000 + 1;
+    dump(arr.join('y'));
+} catch (e) {
+    print(e);
+}