匹配Javascript中的正则表达式

Question

I am using Javascript to validate my form fields, and the below regular expression is not working. Am I using the wrong method to match?

var name=document.getElementById('first_name').value;

if (!name.match(/^[A-Za-z]*$/))
{
    document.getElementById('error').innerHTML = "Please match the regxp";
    document.getElementById('first_name').focus();
    return false;
}

i am executing the above code on form submit.

Answer 1

The * repetition operator matches zero or more occurrences, so the regular expression ^[A-Za-z]*$ will match zero or more occurrences of a letter, ie it will match the empty string as well as a string containing only letters.

You probably meant to use the + repetition operator to match 1 or more like ^[A-Za-z]+$

Answer 2

Try this. Using Regex would do that.

function validateName(x){
    var name=document.getElementById('first_name').value;
    var pattern = new RegExp('/^\w+$/');
    if(!pattern.test(name)){
       alert("Use only A-Z, a-z, 0-9, or _ in names.");
       return false;
    }
}

Answer 3

I'm not sure your problem is in the code you posted, is that bound properly to an event handler?

It works fine in jsfiddle http://jsfiddle.net/dD6y3/

Just added on blur binding, maybe it's what you are missing? or what is wrong? Hard to say without seeing more code.

$('#first_name').on("blur", function() {

  var name = document.getElementById('first_name').value;

    if (!name.match(/^[A-Za-z]*$/)) {
        document.getElementById('error').innerHTML="Please match the regxp";
        document.getElementById('first_name').focus();
        return false;
    }
});

Answer 4

Your regular expression seems to be ok, have you attached the event to the input? You should add the event so as to check whether it's correct or not: http://www.w3schools.com/js/js_htmldom_events.asp

Here's my solution, it checks the error when you deselect the input, when you change to another input:

HTML

<div id='error'></div>
<input id='first_name' onchange="checkChanges()"/>

Although this will work, you should use Event Handlers or a framerowk such as jQuery so as to guarantee it'll work on all possible browsers

JS

function checkChanges() {
var name = document.getElementById('first_name').value;

if (!name.match(/^[A-Za-z]*$/))
{
    document.getElementById('error').innerHTML="Please match the regxp";
    document.getElementById('first_name').focus();
    return false;
} else {
    document.getElementById('error').innerHTML="OK";
}
}

Live Demo

Answer 5

Assuming you want your name to begin with a letter, and you're not using jQuery...

var errors = document.getElementById('error');
var firstName = document.getElementById('first_name');

function validate(element) {
  var name = element.value;
  if (name.match(/^[A-Za-z]+$/)) {
      return true;
  }
  errors.innerHTML = "Name must begin with a letter";
  element.focus();
  return false;
}

validate(firstName);  // needs moving to a submit event handler or similar

Answer 6

I have solved it...

To match a regular expression, I used the below method...

var pattern=/^[A-Za-z0-9]+$/;
if (!pattern.test(document.getElementById('first_name').value))
{
    document.getElementById('error').innerHTML = "only the characters and 0-9 are allowed";
    document.getElementById('first_name').focus();
    return false;
}

By the way, thanks for all your reply