JavaScript我测试密码的功能不起作用

Question

function demoMatchClick() {
  var validString = /^[a-z](?=[a-z]*[0-9])[a-z0-9]{0,6}[a-z]$/
  var re = new RegExp(validString);
  if (document.form1.subject.value.test(re)) {
    alert("Successful match");
  } else {
    alert("No match");
  }
}

<INPUT TYPE=SUBMIT VALUE="Replace" ONCLICK="demoReplaceClick()">

I can't get it to popup an Alert to pop up

I want these rules to be enforced

•Not have upper-case letters. 
•Begin with a letter. 
•Have at least 1 digit(s) not at the beginning and end. 
•Have up to 8 alphanumeric 
•Does NOT have any symbols like @#$ characters (symbols like !@#$%^&*()-+).

I am using a button to execute the code for now.

Answer 1

Here is the modified code:

function demoMatchClick(input) {
  var validString = /^[a-z](?=[a-z]*[0-9])[a-z0-9]{0,6}[a-z]$/;
  if (validString.test(input)) {
    alert("Successful match");
  } else {
    alert("No match");
  }
}


demoMatchClick("hello world");

validString variable is already a RegExp object and you can use it directly, additionally .test() method belongs to regex object not to string.

Answer 2

Well, I suppose this regex suits your rules...

var rules = /^[a-z](?=[a-z]*[0-9])[a-z0-9]{0,6}[a-z]$/;

But I think there are several issues with your code, which I'd like to point out. Don't take it as a personal offense, please: believe me, I'm actually saving you a LOT of time and nerves.

First, there's a standard rule: each function should do only one thing - but do it really well (or so they say, these perfectionists!). Your code is too tightly coupled with DOM extraction: I was really surprised when it failed to work when pasted in my environment! Only then I noticed that document.forms call. It's not really needed here: it's sufficient to build a function taking one parameter, then call this function with the value extracted somewhere else. This way, btw, you can easily separate the causes of errors: it would be either in DOM part, or within the function.

Second, Regexes are really very close to be considered first-class citizens in JavaScript (not so as in Perl, but still much closer than in some other languages). That means you can write the regex literals as is, and use it later - without new Regexp constructs.

With all that said, I'd write your code as...

function validatePassword(password) {
  var rules = /^[a-z](?=[a-z]*[0-9])[a-z0-9]{0,6}[a-z]$/;
  return rules.test(password);
}

... then use it by something like ...

var password = document.form1.subject.value;
alert( validatePassword(password) ? 'Success! :)' : 'Failure... :(' );

PS And yes, Riccardo is right: set too strict rules for passwords - and suffer the consequences of narrowing the range of search for an attacker. And it's quite easy to see the validation rules set in Javascript: even obfuscators won't help much.