func-loc

A simple tool that help you to retrieve the function location from its reference.

How to install

1$ npm i func-loc

How to use

1const { locate } = require('func-loc');
2
3const fn = () => {
4  console.log('Hello there');
5};
6
7(async () => {
8  const result = await locate(fn);
9  console.log(result);
10  // Will result: { source: 'file://__BASE_FOLDER__/func-loc/this-file.js', line: 3, column: 12 }
11})();

APIs

1. locate(fn: Function): Will retrieve the location of a given function, and will cache it so that the second call will be faster.

The result of the call will be an object that contains these attributes:

• source: The source file.
• line: The line where the function was defined.
• column: The exact column where the function was declared.

Internally, this function will open an inspector session. So it is always a good idea to call the disconnect method when you are done.

2. disconnect() : will disconnect the inspector session, cleans the cache and delete temporary created objects from the global object.

Using Source Maps

This library can also locate the original code using source-map:

Lets say that you have a typescript file containing:

1// File: `module.ts`
2export function inner() {
3  const fn3 = () => {};
4  return fn3;
5}

Transpiling this file using typescript compiler will generate a source map file like:

1{
2  "origin": {
3    "path": "/BASE_FOLDER/module.js",
4    "column": 24,
5    "line": 5,
6    "source": "file:///BASE_FOLDER/module.js"
7  },
8  "line": 3,
9  "column": 14,
10  "path": "/BASE_FOLDER/module.ts",
11  "source": "file:///BASE_FOLDER/module.ts"
12}

And a javascript file containing:

1"use strict";
2exports.__esModule = true;
3// File: `module.ts`
4function inner() {
5    var fn3 = function () { };
6    return fn3;
7}
8exports.inner = inner;
9//# sourceMappingURL=module.js.map

If you execute the following code

1const { locate } = require('func-loc');
2const { inner } = require('../__tests__/assets/module');
3
4(async () => {
5  const loc = await locate(inner(), { sourceMap: true });
6  console.log(loc);
7})();

It will output the line of the inner function f3 of the file module.ts:

1{
2  "origin": {
3    "path": "/BASE_FOLDER/module.js",
4    "column": 24,
5    "line": 5,
6    "source": "file:///BASE_FOLDER/module.js"
7  },
8  "line": 3,
9  "column": 14,
10  "path": "/BASE_FOLDER/module.ts",
11  "source": "file:///BASE_FOLDER/module.ts"
12}

License

MIT © Mohamed IDRISSI