Illegal Alphabet Checker

jiancha.js

#!/usr/bin/env node

var content = process.argv[process.argv.length - 1];

if (content == process.title) {
    console.log("Usage: " + process.title + " <content>");
    process.exit();
} else {
	var illegalAlphabet = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ".split("");
	illegalAlphabet.forEach(function(alphabet) {
		if (content.indexOf(alphabet) != -1) {
			console.error("Error! Found illegal alphabet " + alphabet);
		}
	});
}