Develop Reference

Regex for getting only the last N numbers in javascript

I've being trying to generate a regex for this string:
case1: test-123456789 should get 56789
case2: test-1234-123456789 should get 56789
case3: test-12345 should fail or not giving anything
what I need is a way to get only the last 5 numbers from only 9 numbers
so far I did this:
case.match(/\d{5}$/)
it works for the first 2 cases but not for the last one

You may use
/\b\d{4}(\d{5})$/
See the regex demo. Get Group 1 value.
Details
\b - word boundary (to make sure the digit chunks are 9 digit long) - if your digit chunks at the end of the string can contain more, remove \b
\d{4} - four digits
(\d{5}) - Group 1: five digits
$ - end of string.
JS demo:
var strs = ['test-123456789','test-1234-123456789','test-12345'];
var rx = /\b\d{4}(\d{5})$/;
for (var s of strs) {
var m = s.match(rx);
if (m) {
console.log(s, "=>", m[1]);
} else {
console.log("Fail for ", s);
}
}

You can try this:
var test="test-123456789";
console.log((test.match(/[^\d]\d{4}(\d{5})$/)||{1: null/*default value if not found*/})[1]);
This way supports default value for when not found any matching (look at inserted comment inline above code.).

You can use a positive lookbehind (?<= ) to assert that your group of 5 digits is preceeded by a group of 4 digits without including them in the result.
/(?<=\d{4})\d{5}$/
var inputs = [
"test-123456789", // 56789
"test-1234-123456789", // 56789
"test-12345", //fail or not giving anything
]
var rgx = /(?<=\d{4})\d{5}$/
inputs.forEach(str => {
console.log(rgx.exec(str))
})

JavaScript Regex: How to let only 2 decimal floating number through oninput pattern match?

I have an input type="text" with an input event handler attached to it, which i would like to use to overwrite the input.value with a "filtered" result of the users' key presses.
Basically i want to write a regular expression that only allows floating numbers (positive or negative) with (optionally) 2 decimal positions.
Here's a scripted example of what i'm looking for.
If you hit any key while focusing the input in the example above, the input value will be filtered using a combination of regex and JavaScript.
My test input currently looks like this:
<input type="text" id="test" value="-3c.fvbnj23.79.8fbak-cfb436.sdafosd8r32798s.hdf-5kasjfds-gf..">
The input event handler looks like this:
document.getElementById('test').oninput = function(){
var foundDot = false,
str = '';
this.value.replace(/^-|\.(?=\d)|\d*/g, function(match){
if (match === '.' && foundDot === true) {
return;
}
if (match === '.' && foundDot === false) foundDot = true;
str += match;
});
this.value = parseFloat(str).toFixed(2);
}
Is it possible to obtain the same result with a regular expressions only?

Even better, it can be done without regex at all.
Well, okay, one regex. I misunderstood that you wanted to preserve digits within non-numeric strings.
All right, fiiiiine, two regexes. ¯\_(ツ)_/¯
//oninput is too aggressive, it runs on every keystroke making it difficult to type in longer values.
document.getElementById('test').onchange = function(){
// strip non-numeric characters.
// First char can be -, 0-9, or .
// Others can only be 0-9 or .
var val = this.value.replace(/(?!^[\-\d\.])[^\d\.]/g,'');
// strip out extra dots. Here I admit regex defeat and resort to slice-and-dice:
var firstDot = this.value.indexOf('.');
if (firstDot > -1) {
val = val.substr(0,firstDot+1) + val.substring(firstDot+1).replace(/\./g,'')
}
console.log(val);
// Finally the easy part: set the precision
this.value = parseFloat(val).toFixed(2);
}
<input id="test">

I don't know why you can't just use a find/replace on each keystroke.
Find ^([-+]?(?:\d+(?:\.\d{0,2})?|\.\d{0,2})?)
Replace $1
Expanded
^
( # (1 start)
[-+]?
(?:
\d+
(?:
\. \d{0,2}
)?
|
\. \d{0,2}
)?
) # (1 end)

Assistance with a regular expression Javascript

I'm trying to achieve this regular expression check. (1 integer, 3 digits)
Valid:
0.236
0.21
1.231
1.01
Invalid:
12.23
12321
0.21323
I would like to have only 1 digit follow by a decimal with only 0-3 decimal places.
Any help would be great. I have tried this:
^(([0-9]{1})?(?=\.)[0-9]{0,3})|([0-9]{1})$
but no lock.
Edit: I should have added that I'm using a JQuery plugin called inputmask. I would like for the inputmask to only accept my requirement.

To do this with jquery-inputmask, use this
<input id="example2" data-inputmask-regex="/^\d{1}\.\d{0,3}$/" />
And then in your JavaScript file, add this
$(document).ready(function(){
$("#example2").inputmask("Regex");
});
Here is the Regex breakdown
^ - Regex must start with this expression
\d{1} - Exactly 1 digit from 0 to 9
\. - Followed by a period. Important to note that periods must be escaped
\d{0,3} - Followed by 0 to 3 digits
$ - Regex must end with this expression
I tested for all of your examples.

I would like to have only 1 whole number follow by a decimal with only 0-3 decimal places.
By "1 whole number" I take it you mean one digit, as 12 is a single whole number. If so:
\d\.\d{0,3}
That matches a single digit followed by a . followed by zero to three digits. If you want to further assert that it matches the entire string, add anchors to either end:
^\d\.\d{0,3}$
Note that the rules you've given allow for 1., which seems like you may not want. If you don't, then we need to do a bit more work:
^\d(?:\.\d{1,3})?$
That says: One digit optionally followed by a . with 1-3 digits. It has the "whole string" anchors, remove them if you don't want them.
Live Example using that last one:
var input = document.querySelector("input");
var rex = [
/\d\.\d{0,3}/,
/^\d\.\d{0,3}$/,
/^\d(?:\.\d{1,3})?$/
];
input.oninput = input.onpaste = input.onkeypress = updateDisplay;
function updateDisplay() {
rex.forEach(function(r, index) {
var display = document.getElementById("r" + index);
if (!input.value) {
display.innerHTML = "--";
} else if (input.value.match(r)) {
display.innerHTML = "valid";
} else {
display.innerHTML = "INVALID";
}
});
}
<input type="text">
<p><code>/\d\.\d{0,3}/</code> says: <span id="r0"></span></p>
<p><code>/^\d\.\d{0,3}$/</code> says: <span id="r1"></span></p>
<p><code>/^\d(?:\.\d{1,3})?$/</code> says: <span id="r2"></span></p>

Check whether text field contains numbers only and has to be 11 digits

I have this function to check whether the text field contains numbers only, if there are letters in this field then an error should show
//Tel Validate
function is_valid_tel() {
$this = $("#inputTel");
var pattern = new RegExp("^[0-9]*$");
if(pattern.test($this.val())){ // valid
if ($this.closest(".control-group").hasClass("error"))
$this.closest(".control-group").removeClass("error");
$this.siblings(".help-inline").css("display", "none");
return true;
} else { // error
if (!$this.closest(".control-group").hasClass("error"))
$this.closest(".control-group").addClass("error");
$this.siblings(".help-inline").css("display", "block");
return false;
}
}
When i enter letters into the text field i get no error thrown. My jquery/javascript is limited but I thought this would at least work? as the reg exp checks for numbers between 0-9. I would also like to check that if a number is entered then it matches 11 digits
Any help appreciated thanks

use this regular expression ^\d{11}$
old regex
^ begin of string
[0-9]* 0 or more digits
$ end of string
new regex
^ begin of string
\d{11} 11 digits (\d == [0-9])
$ end of string

Try the following RegExp
var pattern = new RegExp("^[0-9]{11}$");
Which is a more readable version of :
var pattern = new RegExp("^\d{11}$");
You will find a handy reference about special characters here.

Javascript regex to match only up to 11 digits, one comma, and 2 digits after it

I have a textbox where I want only allowed up to 11 digits, an optional comma, and two more digits after it. Anything else should not be rendered when the key is pressed into the textbox:
$('#txt').keypress(function (e) {
var code = e.which;
var key = String.fromCharCode(code);
// REGEX TO AVOID CHARS & A DOT (.)
var pattern = /[a-zA-Z]|\./g;
var isMatch = pattern.test(key);
if (isMatch) {
// DO NOT RENDER CHARS & dot
e.preventDefault();
}
});
The above code works when an invalid key is pressed, such as a char or a dot, but does not ensure only one comma and only 2 digits afterwards.
This must match:
12314
123123,44
This must not:
12313,6666
Here is a demo.
UPDATE:
Any digit except numbers and comma must be avoided, so the regex I proposed is not valid since only prevents dots (.).

You should test your complete string, not only the current letter.
$('#txt').keypress(function (e) {
var key = String.fromCharCode(e.which);
var pattern=/^[0-9]{1,11}(,[0-9]{0,2})?$/;
// test this
var txt = $(this).val() + key;
if (!pattern.test(txt)) {
e.preventDefault();
}
});
​
jsfiddle example

This regex will match any string containing 1 up to 11 digits optionally followed by a , and exactly 2 more digits: ^[0-9]{1,11}(,[0-9]{2})?$
Explanation:
^ # Match the start of the string
[0-9]{1,11} # Followed by a maximum of 11 digits
(,[0-9]{2})? # Optionally followed by a comma and 2 more digits
$ # Followed by the end of the string
See it in action here.