jquery - Validating Dimension text input javascript -

how validate asp textbox javascript. want validate users input 4-1/2 or 80-1/2 or 6/8 or 5. there types of patterns there allowed , contains 1 number. want show alert when input doesn't match.
beginner javascript.

my code tried.

function valid_dimentions(fieldobj) {  // regular expression  var rgexp = new regexp(""/^[0-9/-]{1,4}$/"");  var input = fieldobj.value;      if (input.match(rgexp))          alert("the width field format incorrect!");                     } 

i used money , works , used build non working code.

function valid_number(fieldobj) {  if (fieldobj.value != '' && isnan(fieldobj.value)) {     alert('you must enter valid price 0.00 , no $');     fieldobj.select();     fieldobj.focus();     return false;  }  return true; } 

...

<asp:textbox id="twidth" type="text" runat="server" placeholder="4-1/2" onchange="valid_dimentions_width(this);"  list="parttype" runat="server" required="required" width="210px" autocompletetype="disabled" autopostback="true"/> 

• avoid using alert. instead, fill element error message.
• avoid validating on client only, validate on server side well.
• your if displaying error when match true. should negate it.
• your regex wrong, it's checking if it's 1 4 digit number.
• you can declare regex enclosing between /'s

here's regex came with:

^([0-9]+|[0-9]+-[0-9]+\/[0-9]+|[0-9]+\/[0-9]+)$ 

it checks if number 1 of following:

• pure number: [0-9]+
• number folowed - followed number/number: [0-9]+-[0-9]+\/[0-9]+
• number/number: [0-9]+\/[0-9]+

see have scape / \ regex definition not messed up.

here's final code:

function valid_dimensions_width(fieldobj) {     var error = ""     var rgexp = /^([0-9]+|[0-9]+-[0-9]+\/[0-9]+|[0-9]+\/[0-9]+)$/;     var input = fieldobj.value;     if (!input.match(rgexp)) error = "the width field format incorrect!";     document.getelementbyid("twidtherror").innerhtml = error; } 

and working fiddle: http://jsfiddle.net/w3f5skp8/

i replaced onchange onkeyup shows feedback instantly.