How do I make + only appear once and at the front only like example +01234564789 in regex jquery.

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How do I make + only appear once and at the front only like example +01234564789 in Regex Jquery. The character can't be everywhere and only front and appear only once in the textfield.

What I have tried:

I have try this, but its still have problem. So I really need help I'm a beginner for this so please help me.

$(function(){
$('#hpno').keypress(function(e){
var txt = String.fromCharCode(e.which);
console.log(txt + ' : ' + e.which);
if(!txt.match(/^\+*/ [0-9]+$/))
{
return false;
}
});
});

Posted 22-Aug-18 19:13pm

Member 13951173

Updated 22-Aug-18 19:45pm

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OriginalGriff · Answer 1 · 2018-08-22T19:44:00

Solution 1

Try:

^\+?\d*$

If you want to work with regexes, then get a copy of Expresso[^] - it's free, and it examines and generates Regular expressions.

Posted 22-Aug-18 19:44pm

OriginalGriff

v2

Patrice T · Answer 2 · 2018-08-22T19:45:00

Quote:
How do I make + only appear once and at the front only like example +01234564789 in Regex Jquery.

I think your problem is that you have not understood that your code is launch on keypress.
This imply that your RegEx have to match partial input or empty input.
This mean that your RegEx must match:

C++

'' // Empty textbox
'+' // + sign
'9' // a single digit
'+9' // + and a single digit
'9...9'  // many digits
'+9...9'

You need to rethink your RegEx, and probably check the full input at the end since the keypress can't enforce a minimum number of digits.

By the way * is for 'zero or more' RegEx sign, you need to use 'zero or 1' RegEx sign.

Just a few interesting links to help building and debugging RegEx.
Here is a link to RegEx documentation:
perlre - perldoc.perl.org[^]
Here is links to tools to help build RegEx and debug them:
.NET Regex Tester - Regex Storm[^]
Expresso Regular Expression Tool[^]
RegExr: Learn, Build, & Test RegEx[^]
Online regex tester and debugger: PHP, PCRE, Python, Golang and JavaScript[^]
This one show you the RegEx as a nice graph which is really helpful to understand what is doing a RegEx:
Debuggex: Online visual regex tester. JavaScript, Python, and PCRE.[^]
This site also show the Regex in a nice graph but can't test what match the RegEx:
Regexper[^]