stdlib-js
<summary>
About stdlib...
</summary>
We believe in a future in which the web is a preferred environment for numerical computation. To help realize this future, we've built stdlib. stdlib is a standard library, with an emphasis on numerical and scientific computation, written in JavaScript (and C) for execution in browsers and in Node.js.
The library is fully decomposable, being architected in such a way that you can swap out and mix and match APIs and functionality to cater to your exact preferences and use cases.
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Exists
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Test whether a path exists on the filesystem.
bash
npm install @stdlib/fs-exists
javascript
var exists = require( '@stdlib/fs-exists' );
#### exists( path, clbk )
Asynchronously tests whether a path exists on the filesystem.
javascript
exists( __dirname, done );
function done( bool ) {
if ( bool ) {
console.log( '...path exists.' );
} else {
console.log( '...path does not exist.' );
}
}
The above callback signature matches the now deprecated [fs.exists()][node-fs-exists] API. The function also accepts the more conventional error-first style callback signature found in most asynchronous Node APIs.
javascript
exists( __dirname, done );
function done( error, bool ) {
if ( error ) {
console.error( error.message );
}
if ( bool ) {
console.log( '...path exists.' );
} else {
console.log( '...path does not exist.' );
}
}
#### exists.sync( path )
Synchronously tests whether a path exists on the filesystem.
javascript
var bool = exists.sync( __dirname );
// returns <boolean>
javascript
var path = require( 'path' );
var readFileSync = require( '@stdlib/fs-read-file' ).sync;
var file = path.join( __dirname, 'foo.js' );
if ( exists.sync( __dirname ) ) {
file = readFileSync( file );
}
Because time elapses between checking for existence and performing IO, at the time IO is performed, the path is no longer guaranteed to exist. In other words, a race condition exists between the process attempting to read and another process attempting to delete.
Instead, the following pattern is preferred, where errors are handled explicitly:
javascript
var path = require( 'path' );
var readFileSync = require( '@stdlib/fs-read-file' ).sync;
var file = path.join( __dirname, 'foo.js' );
try {
file = readFileSync( file );
} catch ( error ) {
console.log( 'unable to read file.' );
console.error( error );
}
- Nevertheless, use cases exist where one desires to check existence without performing IO. For example,
javascript
var path = require( 'path' );
var writeFileSync = require( '@stdlib/fs-write-file' ).sync;
var file = path.join( __dirname, 'foo.js' );
if ( exists.sync( file ) ) {
console.log( 'Don\'t overwrite the file!' );
} else {
writeFileSync( file, 'beep', {
'encoding': 'utf8'
});
}
javascript
var exists = require( '@stdlib/fs-exists' );
/* Sync */
console.log( exists.sync( __dirname ) );
// => true
console.log( exists.sync( 'beepboop' ) );
// => false
/* Async */
exists( __dirname, done );
exists( 'beepboop', done );
function done( error, bool ) {
if ( error ) {
console.error( error.message );
} else {
console.log( bool );
}
}
@stdlib/fs-exists-cli][@stdlib/fs-exists-cli]: CLI package for use as a command-line utility.
- [@stdlib/fs-read-file][@stdlib/fs/read-file]: read the entire contents of a file.
- [@stdlib/fs-read-dir][@stdlib/fs/read-dir]: read the entire contents of a directory.
