Like the unix which utility.

Finds the first instance of a specified executable in the PATH environment variable. Does not cache the results, so hash -r is not needed when the PATH changes.

const which = require('which')
// async usage
// rejects if not found
const resolved = await which('node')
// if nothrow option is used, returns null if not found
const resolvedOrNull = await which('node', { nothrow: true })
// sync usage
// throws if not found
const resolved = which.sync('node')
// if nothrow option is used, returns null if not found
const resolvedOrNull = which.sync('node', { nothrow: true })
// Pass options to override the PATH and PATHEXT environment vars.
await which('node', { path: someOtherPath, pathExt: somePathExt })

Just like the BSD which(1) binary but using node-which.

usage: node-which [-as] program ...

You can learn more about why the binary is node-which and not which here

You may pass an options object as the second argument.

• path: Use instead of the PATH environment variable.
• pathExt: Use instead of the PATHEXT environment variable.
• all: Return all matches, instead of just the first one. Note that this means the function returns an array of strings instead of a single string.