gistfile1.js

var one = 'http://blah'
  , two = '/asdf/asdf/af'
  ;

function regexTest () {
  var start = new Date();
  var i = 0;
  while (i<1000000) {
    if ( !/^http?:/.test(one) ) true
    if ( !/^http?:/.test(two) ) true
    i++;
  }
  var end = new Date();
  console.log('regexTest: '+(end - start))
}

function sliceTest () {
  var start = new Date();
  var i = 0;
  while (i<1000000) {
    if (one.slice(0, 'http'.length) === 'http') true
    if (two.slice(0, 'http'.length) === 'http') true
    i++
  }
  var end = new Date();
  console.log('sliceTest: '+(end - start))
}

regexTest();
sliceTest();