Function that checks if a number is Hex with Javascript (ES5)

isHex.js

var compose = function() {
  var funcs = Array.prototype.slice.apply(arguments);
  return function(arg) {
    return funcs.reduce(function(arg, fn) {
      return fn.call(this, arg);
    }, arg);
  };
};

var and = function() {
  return Array.prototype.slice.apply(arguments).reduce(function(prev, curr) { return prev&&curr; });
}

var parseHex = function(v) {
  return parseInt(v, 16);
};

var isHex = function(str) {
  str = str.split('');
  var parseHexIsFinite = compose(parseHex, isFinite);
  return str.map(parseHexIsFinite).reduce(and);
}

function isHex(str) {
  return /^[A-F0-9]+$/i.test(str)
}

Should be most performant and easy to understand.

function isHex(str) {
  return /^[A-F0-9]+$/i.test(str)
}

Should be most performant and easy to understand.

That right there is the best solution. Not sure why I didn't think of doing it with regex to begin with :-)
Thanks