title: How to check if a JavaScript number is a real, valid number?
body: <p>MY code is:</p>
  
  <pre><code>function isNumber(n){
  return typeof n == 'number' &amp;&amp; !isNaN(n);
  }
  
  window.onload=function(){
  var a=0,b=1,c=2.2,d=-3,e=-4.4,f=10/3;
  var shouldBeTrue=[a,b,c,d,e,f];
  
  var aa="0",bb="1",cc="2.2",dd="-3",ee="-4.4",ff="10/3";
  var shouldBeFalse=[aa,bb,cc,dd,ee,ff];
  
  var aaa,bbb=true,ccc=false,ddd=document.getElementsByTagName('html');
  var alsoTheseBeFalse=[aaa,bbb,ccc,ddd,""," ",,null,NaN];
  
  for(var i=0;i&lt;shouldBeTrue.length;i++)
      if(isNumber(shouldBeTrue[i]) != true) alert("x");
  for(i=0;i&lt;shouldBeFalse.length;i++)
      if(isNumber(shouldBeFalse[i]) != false) alert("x");
  for(i=0;i&lt;alsoTheseBeFalse.length;i++)
      if(isNumber(alsoTheseBeFalse[i]) != false) alert("x");
  }
  </code></pre>
  
  <p>What else should I check against to ensure my function is 101% perfect in all ways? (also, if you know a better function please tell me)</p>