# Improvements to JavaScript analysis

## General improvements

* Suppor for `globalThis` has been added.

* Support for the following frameworks and libraries has been improved:
  - [firebase](https://www.npmjs.com/package/firebase)
  - [mongodb](https://www.npmjs.com/package/mongodb)
  - [mongoose](https://www.npmjs.com/package/mongoose)
  - [rate-limiter-flexible](https://www.npmjs.com/package/rate-limiter-flexible)

* The call graph has been improved to resolve method calls in more cases. This may produce more security alerts.

* TypeScript 3.6 features are supported.


## New queries

| **Query**                                                                 | **Tags**                                                          | **Purpose**                                                                                                                                                                            |
|---------------------------------------------------------------------------|-------------------------------------------------------------------|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| Unused index variable (`js/unused-index-variable`)                        | correctness                                                       | Highlights loops that iterate over an array, but do not use the index variable to access array elements, indicating a possible typo or logic error. Results are shown on LGTM by default. |
| Loop bound injection (`js/loop-bound-injection`)                          | security, external/cwe/cwe-834                                      | Highlights loops where a user-controlled object with an arbitrary .length value can trick the server to loop indefinitely. Results are shown on LGTM by default. |
| Suspicious method name (`js/suspicious-method-name-declaration`)          | correctness, typescript, methods                                  | Highlights suspiciously named methods where the developer likely meant to write a constructor or function. Results are shown on LGTM by default. |
| Shell command built from environment values (`js/shell-command-injection-from-environment`) | correctness, security, external/cwe/cwe-078, external/cwe/cwe-088 | Highlights shell commands that may change behavior inadvertently depending on the execution environment, indicating a possible violation of [CWE-78](https://cwe.mitre.org/data/definitions/78.html). Results are shown on LGTM by default.|
| Use of returnless function (`js/use-of-returnless-function`)              | maintainability, correctness                                      | Highlights calls where the return value is used, but the callee never returns a value. Results are shown on LGTM by default. |
| Useless regular expression character escape (`js/useless-regexp-character-escape`) | correctness, security, external/cwe/cwe-20 | Highlights regular expression strings with useless character escapes, indicating a possible violation of [CWE-20](https://cwe.mitre.org/data/definitions/20.html). Results are shown on LGTM by default. |
| Unreachable method overloads (`js/unreachable-method-overloads`)          | correctness, typescript                                           | Highlights method overloads that are impossible to use from client code. Results are shown on LGTM by default. |

## Changes to existing queries

| **Query**                      | **Expected impact**          | **Change**                                                                |
|--------------------------------|------------------------------|---------------------------------------------------------------------------|
| Incomplete string escaping or encoding (`js/incomplete-sanitization`) | Fewer false-positive results | This rule now recognizes additional ways delimiters can be stripped away. |
| Client-side cross-site scripting (`js/xss`) | More results, fewer false-positive results | More potential vulnerabilities involving functions that manipulate DOM attributes are now recognized, and more sanitizers are detected. |
| Code injection (`js/code-injection`) | More results | More potential vulnerabilities involving functions that manipulate DOM event handler attributes are now recognized. |
| Hard-coded credentials (`js/hardcoded-credentials`) | Fewer false-positive results | This rule now flags fewer password examples. |
| Illegal invocation (`js/illegal-invocation`) | Fewer false-positive results | This rule now correctly handles methods named `call` and `apply`. |
| Incorrect suffix check (`js/incorrect-suffix-check`) | Fewer false-positive results | The query recognizes valid checks in more cases. |
| Network data written to file (`js/http-to-file-access`) | Fewer false-positive results | This query has been renamed to better match its intended purpose, and now only considers network data untrusted. | 
| Password in configuration file (`js/password-in-configuration-file`) | Fewer false-positive results | This rule now flags fewer password examples. |
| Prototype pollution (`js/prototype-pollution`) | More results | The query now highlights vulnerable uses of jQuery and Angular, and the results are shown on LGTM by default. |
| Reflected cross-site scripting (`js/reflected-xss`) | Fewer false-positive results | The query now recognizes more sanitizers. |
| Stored cross-site scripting (`js/stored-xss`) | Fewer false-positive results | The query now recognizes more sanitizers. |
| Uncontrolled command line (`js/command-line-injection`) | More results | This query now treats responses from servers as untrusted. |
| Uncontrolled data used in path expression (`js/path-injection`) | Fewer false-positive results | This query now recognizes calls to Express `sendFile` as safe in some cases. |
| Unknown directive (`js/unknown-directive`) | Fewer false positive results | This query no longer flags uses of ":", which is sometimes used like a directive. |

## Changes to libraries

* `Expr.getDocumentation()` now handles chain assignments.

## Removal of deprecated queries

The following queries (deprecated since 1.17) are no longer available in the distribution:

* Builtin redefined (js/builtin-redefinition)
* Inefficient method definition (js/method-definition-in-constructor)
* Bad parity check (js/incomplete-parity-check)
* Potentially misspelled property or variable name (js/wrong-capitalization)
* Unknown JSDoc tag (js/jsdoc/unknown-tag-type)
* Invalid JSLint directive (js/jslint/invalid-directive)
* Malformed JSLint directive (js/jslint/malformed-directive)
* Use of HTML comments (js/html-comment)
* Multi-line string literal (js/multi-line-string)
* Octal literal (js/octal-literal)
* Reserved word used as variable name (js/use-of-reserved-word)
* Trailing comma in array or object expressions (js/trailing-comma-in-array-or-object)
* Call to parseInt without radix (js/parseint-without-radix)