cli.js

// Regular commander.js logic up here. None of this
// logic is run if a subcommand match was found 


var knownSubCommands = [
      "blah",
      "ha",
      "etc"
    ]

// Detect if the sub command was missspelled
var found;
knownSubCommands.forEach( function(subCommand) {
    if(process.argv[2] === subCommand){
        found = true;
    }
});

// Not found, notify user of their miss spelling and suggest the closest match
// and how to find the list of commands
if(!found){
    var hamming = require( 'compute-hamming' ),
        closestSubCommands = [];

    // First try to find if any commands start with the letters of the arg
    knownSubCommands.forEach( function(subCommand) {
        if(subCommand.search(process.argv[2]) === 0){
            closestSubCommands.push(subCommand);
        }
    });

    if(closestSubCommands.length === 0){

        // Find the closest match
        var closestDistance = Number.MAX_SAFE_INTEGER;
        knownSubCommands.forEach( function(subCommand) {
            // hamming() requires the commands to be of the same length. So we need to
            // to clip the longer one and consider each clipped character to be one edit
            var string1 = subCommand,
                string2 = process.argv[2],
                distance = 0;

            if(string1.length < string2.length){
                distance = string2.length - string1.length;
                string2 = string2.slice(0,string1.length);

            } else if(string1.length > string2.length){
                distance = string1.length - string2.length;
                string1 = string2.slice(0, string2.length);
            }

            distance += hamming(string1, string2);

            if( distance < closestDistance){
                closestDistance = distance;
                closestSubCommands = [subCommand];
            }
        });
    }

    console.log("jibo: '" + process.argv[2] + "' is not a jibo command. See 'jibo --help' for the list of commands.");
    console.log("");

    if(closestSubCommands.length === 0){
        console.log("Did you mean this?");
    } else {
        console.log("Did you mean one of these?");
    }

    closestSubCommands.forEach( function(subCommand){
        console.log("   " + subCommand);
    });
}

package.json

{
  "dependencies": {
    "compute-hamming": "^1.1.0"
  }
}