Move dmenuPath outside the function declaration and use camelCase like the rest of the project.

src/exec-dmenu.js

@@ -1,5 +1,7 @@
 const { exec } = require('child_process')
 
+const dmenuPath = process.env.DMENU_PATH || 'dmenu'
+
 module.exports = (...args) => choices =>
   new Promise((resolve, reject) => {
     let choice = ''
@@ -7,8 +9,7 @@ module.exports = (...args) => choices =>
     const error = []
 
     // Use a default of 'dmenu' if not specified in process.env
-    const dmenu_binary = (typeof dmenu_path === 'undefined') ? 'dmenu' : dmenu_path;
-    const execCommand = `${dmenu_binary} ${args}`
+    const execCommand = `${dmenuPath} ${args}`
     console.debug('$', execCommand)
     const dmenu = exec(execCommand)
     dmenu.stdin.write(choices)