vue hello world项目
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# is-file-esm
> Determines whether a Node file is a Module (`import`) or a Script (`require`)
## Algorithm
Determining the module system of a file comes from three inputs, the `type` field
of the closest `package.json` to that file, the file extension (`.js`, `.mjs` or `.cjs`)
and the lesser know `--input-type` command-line flag. The latter only applies to
dyamic input (via STDIN, `--eval` or `--print` flags) so is not considered with this library.
So to determine whether a file is an esm file (e.g. native EcmaScript modules) or not,
we use the following procedure:
```
read package.json for "type" field,
if type is "module"
if answer.mjs -> module
if answer.js -> module
if answer.cjs -> script
if type is "commonjs"
if answer.mjs -> module
if answer.js -> script
if answer.cjs -> script
if type is not set
if answer.mjs -> module
if answer.js -> script
if answer.cjs -> script
```
## API
The `is-file-esm` module provides synchronous, awaitable (promise-based) and callback based APIs.
In each case the Result object has the following shape:
```js
{
esm: Boolean, // true if file is a Module, false if it is a Script
type: String, // the determined package.json type, may be undefined, 'module', or 'commonjs'
extType: String, // the file extension type, may be 'c', 'm' or 'j'
path: String, // the input path
pkgPath: String // the path to the package.json from which the type was determined
}
```
### Awaitable (promise-based)
#### `await isFileEsm(path) => Result`
```js
import isFileEsm from 'is-file-esm'
const { esm, path } = await isFileEsm('/path/to/file.js')
if (esm) console.log(`File ${path} is a Module`)
else console.log(`File ${path} is a Script`)
```
### Callback-style
#### `isFileEsm(path, cb(err, Result))`
```js
const isFileEsm = require('is-file-esm')
isFileEsm('/path/to/file.js', (err, result) => {
if (err) {
console.error(err)
return
}
if (result.esm) console.log(`File ${result.path} is a Module`)
else console.log(`File ${result.path} is a Script`)
})
```
### Synchronous
#### `isFileEsm.sync(path) => Result`
```js
import isFileEsm from 'is-file-esm'
const { esm, path } = isFileEsm.sync('/path/to/file.js')
if (esm) console.log(`File ${path} is a Module`)
else console.log(`File ${path} is a Script`)
```
### Test
```sh
npm test
```
```
test/index.js ..................................... 213/213
total ............................................. 213/213
213 passing (927.584ms)
ok
----------|----------|----------|----------|----------|-------------------|
File | % Stmts | % Branch | % Funcs | % Lines | Uncovered Line #s |
----------|----------|----------|----------|----------|-------------------|
All files | 100 | 100 | 100 | 100 | |
index.js | 100 | 100 | 100 | 100 | |
----------|----------|----------|----------|----------|-------------------|
```
### License
MIT