define: DUK_OPT_NO_NONSTD_ARRAY_CONCAT_TRAILER introduced: 1.0.0 tags: - ecmascript description: > For better compatibility with existing code, Array.prototype.concat() has non-standard behavior by default for trailing non-existent elements of the concat result, see https://github.com/svaarala/duktape/blob/master/ecmascript-testcases/test-bi-array-proto-concat-nonstd-trailing.js. If this option is given, concat() will behave in a strictly conforming fashion, ignoring non-existent trailing elements in the result length.