Does trailing dash in a regexp over-match?

dash-regexp.js

var unescaped = new RegExp('^[0-9_-]+$');
var escaped = new RegExp('^[0-9_\\-]+$');
var literal = /^[0-9_-]+$/;

// _ is 0x5f, a is 0x61.  If "_-" over-matches then "a_" will match the above.
var test = "a_";
console.log("unescaped:", test.match(unescaped));
console.log("escaped:", test.match(escaped));
console.log("literal:", test.match(literal));