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Thread: Regex Date Validation

  1. #1

    Thread Starter
    Super Moderator RobDog888's Avatar
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    Regex Date Validation

    Im using this string in javascript to validate a date field upon blur event. Im no regex expert but what am I missing that is keeping this from working? I need it to validate a mm/dd/yyyy, m/d/yyyy, mm/d/yyyy, m/dd/yyyy and also to include leap year.

    This is the string I have so far but it lets 13/10,2020 pass.

    Code:
    ((0?|0[13578]|1[02])[\/.](0[1-9]|[12][0-9]|3[01])[\/.](19|20)[0-9]{2})
    |
    ((0?|0[469]|11)[\/.](0[1-9]|[12][0-9]|30)[\/.](19|20)[0-9]{2})|((02)[\/.](0[1-9]|1[0-9]|2[0-8])[\/.](19|20)[0-9]{2})
    |
    ((2)|(02)[\/.]29[\/.](((19|20)(04|08|[2468][048]|[13579][26]))|2000))

    Think this should work for just the month validation (13578 months only to break this down simplier)?
    (([13578])|0[13578]|1[02])

    Thanks
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  2. #2

    Thread Starter
    Super Moderator RobDog888's Avatar
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    Re: Regex Date Validation

    This works without leap year

    Code:
    ^((0?[13578]|10|12)(-|\/)(([1-9])|(0[1-9])|([12])([0-9]?)|(3[01]?))(-|\/)((19|20)([0-9])(\d{1})|(20)([01])(\d{1})|([8901])(\d{1}))
    |
    (0?[2469]|11)(-|\/)(([1-9])|(0[1-9])|([12])([0-9]?)|(3[0]?))(-|\/)((19|20)([0-9])(\d{1})|(20)([01])(\d{1})|([8901])(\d{1})))$
    VB/Office Guru™ (AKA: Gangsta Yoda®)
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    If a post has helped you then Please Rate it!
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  3. #3

    Re: Regex Date Validation

    HTML

    Code:
    <form>
        <p>Enter date</p>
            <input type="text" id="test1" value="22.05.2013 11:23:22"/>
       
    </form>
    JS

    Code:
    $(document).ready(function(){
        $('#test1').blur(function(){
            if (is_valid_date($(this).val())) {
                $(this).css('background', '#dfd');
            } else {
                $(this).css('background', '#fdd');
            }
        });
    });
    
    function is_valid_date(value) {
        // capture all the parts
        var matches = value.match(/^(\d{2})\.(\d{2})\.(\d{4}) (\d{2}):(\d{2}):(\d{2})$/);
        if (matches === null) {
            return false;
        } else{
            // now lets check the date sanity
            var year = parseInt(matches[3], 10);
            var month = parseInt(matches[2], 10) - 1; // months are 0-11
            var day = parseInt(matches[1], 10);
            var hour = parseInt(matches[4], 10);
            var minute = parseInt(matches[5], 10);
            var second = parseInt(matches[6], 10);
            var date = new Date(year, month, day, hour, minute, second);
            if (date.getFullYear() !== year
              || date.getMonth() != month
              || date.getDate() !== day
              || date.getHours() !== hour
              || date.getMinutes() !== minute
              || date.getSeconds() !== second
            ) {
               return false;
            } else {
               return true;
            }
        
        }
    }
    Try like this!!!

  4. #4
    Super Moderator dday9's Avatar
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    Re: Regex Date Validation

    I would not try to reinvent the wheel. MomentJS is a reliable library that allows you to parse, validate, manipulate, and display dates/times in JavaScript.

    In this case, it would be as simple as:
    Code:
    const inputBlur = function(e) {
        const value = e.target.value;
        const conversion = moment(value);
    
        console.log(`${value} is valid: ${conversion.isValid()}`);
    }
    Fiddle: Live Demo

  5. #5
    PowerPoster kfcSmitty's Avatar
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    Re: Regex Date Validation

    You should always specify a format when using momentJS's isValid(), as well as specifying strict, otherwise you can have unexpected outcomes.

    For example, your example above would return true for the value of

    "it is 12/25/25"

    So you would need to do a conversion for each format you expect, but for just MM/DD/YYYY it would instead be:

    Code:
    const inputBlur = function(e) {
        const value = e.target.value;
        const conversion = moment(value, 'MM/DD/YYYY', true);
    
        console.log(`${value} is valid: ${conversion.isValid()}`);
    }

  6. #6
    Super Moderator dday9's Avatar
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    Re: Regex Date Validation

    That's good to know, thank you kfcSmitty.

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