alert(/^12/.test("12sddaas")); //true
alert(/^12/.test("312ssddd")); //false
alert(/[a-z]{2}$/.exec("312ssddd")[0]); //dd
alert(/[a-z]{2}/.exec("312ssddd")[0]); //ss
alert("sddaas\nsssss\n3333".match(/^[a-z]{2}/gm).join(" ")); //sd ss
alert("sddaas\nsssss\n3333".match(/^[a-z]{2}/g).join(" ")); //sd
alert("sddaas\nsss35\n3333".match(/\d{2}$/gm).join(" ")); //35 33

<pre>
f = str.match(re)
 re = ???

 str = "+=43534"
 f = null

 str = "++2323"
 f = "null"

 str = "=343434"
 f = null

 str = "dsfsdf"
 f = "dsfsdf"

 str = "=43gfvb"
 f = "gfvb"

 str = "+====+"
 f = "===+"
</pre>

<script type="text/javascript">
function TstFunc()  {
 var a = document.getElementById('Input');
 var str = a.value;
  var str2= str.replace(/(\+?[\+=]\d*)/i,'')
 var str2=RegExp["$1"]
 alert(str2)
}
</script>
<input id="Input" type="text"  value="+=43534"><input type="button" value="Test" onclick="TstFunc()">