func-loc

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

How to install

``bash
$ npm i func-loc
`

How to use

`javascript
const { locate } = require('func-loc');

const fn = () => {
console.log('Hello there');
};

(async () => {
const result = await locate(fn);
console.log(result);
// Will result: { source: 'file://__BASE_FOLDER__/func-loc/this-file.js', line: 3, column: 12 }
})();
`

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:

`typescript
// File: module.ts
export function inner() {
const fn3 = () => {};
return fn3;
}
`

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

`json
{
"origin": {
"path": "/BASE_FOLDER/module.js",
"column": 24,
"line": 5,
"source": "file:///BASE_FOLDER/module.js"
},
"line": 3,
"column": 14,
"path": "/BASE_FOLDER/module.ts",
"source": "file:///BASE_FOLDER/module.ts"
}
`

And a javascript file containing:

`javascript
"use strict";
exports.__esModule = true;
// File: module.ts
function inner() {
var fn3 = function () { };
return fn3;
}
exports.inner = inner;
//# sourceMappingURL=module.js.map
`

If you execute the following code

`javascript
const { locate } = require('func-loc');
const { inner } = require('../__tests__/assets/module');

(async () => {
const loc = await locate(inner(), { sourceMap: true });
console.log(loc);
})();
`

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

`json
{
"origin": {
"path": "/BASE_FOLDER/module.js",
"column": 24,
"line": 5,
"source": "file:///BASE_FOLDER/module.js"
},
"line": 3,
"column": 14,
"path": "/BASE_FOLDER/module.ts",
"source": "file:///BASE_FOLDER/module.ts"
}
``

License

MIT © Mohamed IDRISSI

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