RegEx for Javascript to allow only alphanumeric

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I need to find a reg ex that only allows alphanumeric. So far, everyone I try only works if the string is alphanumeric, meaning contains both a letter and a number. I just w

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生来不讨喜

2020-11-22 15:20

Extend the string prototype to use throughout your project

    String.prototype.alphaNumeric = function() {
        return this.replace(/[^a-z0-9]/gi,'');
    }

Usage:

    "I don't know what to say?".alphaNumeric();
    //Idontknowwhattosay

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一生所求

2020-11-22 15:24
```
/^([a-zA-Z0-9 _-]+)$/
```
the above regex allows spaces in side a string and restrict special characters.It Only allows a-z, A-Z, 0-9, Space, Underscore and dash.
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北荒

2020-11-22 15:24
It seems like many users have noticed this these regular expressions will almost certainly fail unless we are strictly working in English. But I think there is an easy way forward that would not be so limited.
1. make a copy of your string in all UPPERCASE
2. make a second copy in all lowercase
Any characters that match in those strings are definitely not alphabetic in nature.
```
let copy1 = originalString.toUpperCase();
let copy2 = originalString.toLowerCase();
for(let i=0; i<originalString.length; i++) {
    let bIsAlphabetic = (copy1[i] != copy2[i]);
}
```
Optionally, you can also detect numerics by just looking for digits 0 to 9.
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误落风尘

2020-11-22 15:24

Question is old, but it's never too late to answer

$(document).ready(function() {
  //prevent paste
  var usern_paste = document.getElementById('yourid');
  usern_paste.onpaste = e => e.preventDefault();

  //prevent copy
  var usern_drop = document.getElementById('yourid');
  usern_drop.ondrop = e => e.preventDefault();
});

$('#yourid').keypress(function (e) {
  var regex = new RegExp("^[a-zA-Z0-9\s]");
  var str = String.fromCharCode(!e.charCode ? e.which : e.charCode);
  if (regex.test(str)) {
      return true;
  }
  e.preventDefault();
  return false;
});

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我在风中等你

2020-11-22 15:26

Jquery to accept only NUMBERS, ALPHABETS and SPECIAL CHARECTERS

<html>
<head>
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
</head>

<body>
Enter Only Numbers: 
<input type="text" id="onlynumbers">
<br><br>
Enter Only Alphabets: 
<input type="text" id="onlyalpha">
<br><br>
Enter other than Alphabets and numbers like special characters: 
<input type="text" id="speclchar">

<script>
    $('#onlynumbers').keypress(function(e) {
      var letters=/^[0-9]/g; //g means global
      if(!(e.key).match(letters)) e.preventDefault();
	});
    
    $('#onlyalpha').keypress(function(e) {
      var letters=/^[a-z]/gi; //i means ignorecase
      if(!(e.key).match(letters)) e.preventDefault();
	});
    
    $('#speclchar').keypress(function(e) {
      var letters=/^[0-9a-z]/gi; 
      if((e.key).match(letters)) e.preventDefault();
	});
    </script>
</body>
</html>

**JQUERY to accept only NUMBERS , ALPHABETS and SPECIAL CHARACTERS **


<!DOCTYPE html>
    $('#onlynumbers').keypress(function(e) {
      var letters=/^[0-9]/g; //g means global
      if(!(e.key).match(letters)) e.preventDefault();
    });

    $('#onlyalpha').keypress(function(e) {
      var letters=/^[a-z]/gi; //i means ignorecase
      if(!(e.key).match(letters)) e.preventDefault();
    });

    $('#speclchar').keypress(function(e) {
      var letters=/^[0-9a-z]/gi; 
      if((e.key).match(letters)) e.preventDefault();
    });

<html>
<head>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.4.1/jquery.min.js">

Enter Only Numbers:

Enter Only Alphabets:

Enter other than Alphabets and numbers like special characters:

</body>
</html>

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一整个雨季

2020-11-22 15:28
Alphanumeric with case sensitive:
```
if (/^[a-zA-Z0-9]+$/.test("SoS007")) {
  alert("match")
}
```
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