单一功能中有多个RegExp

Question

This is not exactly a problem, but more a question of method. I am working on a project where people are able to type shorthand dates in input field, for example if you simply type "20", the input will automatically display the full date for 20th of this month. There are many shorthand types possible, so I had to make multiple RegExp and then check each and every one.

My question is, is there a better way to deal with this? I am no javaScript expert,but I have a feeling that this is not exacty "best practise".

Here is the function

    function dateParser(date) {
            var splitDate = date.split(/[.:\s]/);
            var day = new RegExp(/\b\d{1,2}\b/);
            var dateHour = new RegExp(/\b\d{1,2}\s\d{1,2}\b/);
            var dateHourMin = new RegExp(/\b\d{1,2}\s\d{1,2}[:]\d{1,2}\b/);
            var dateMonth = new RegExp(/\b\d{1,2}[\/\-\,\.]\d{1,2}\b/);
            var dateMonthHour = new RegExp(/\b\d{1,2}[\/\-\,\.]\d{1,2}\s\d{1,2}\b/);
            var dateMonthHourMin = new RegExp(/\b\d{1,2}[\/\-\,\.]\d{1,2}\s\d{1,2}[:]\d{1,2}\b/);
            var dateMonthYear = new RegExp(/\b\d{1,2}[\/\-\,\.]\d{1,2}[\/\-\,\.]\d{1,4}\b/);
            var dateMonthYearHour = new RegExp(/\b\d{1,2}[\/\-\,\.]\d{1,2}[\/\-\,\.]\d{1,4}\s\d{1,2}\b/);
            var dateMonthYearHourMin = new RegExp(/\b\d{1,2}[\/\-\,\.]\d{1,2}[\/\-\,\.]\d{1,4}\s\d{1,2}[:]\d{1,2}\b/);
            var month = new Date().getMonth() + 1;
            var year = new Date().getFullYear();

            var newDate;
            if(dateMonthYearHourMin.test(date)) {
                newDate = splitDate[0]+"."+splitDate[1]+"."+splitDate[2]+" "+splitDate[3]+":"+splitDate[4];
            }
            else if(dateMonthYearHour.test(date)) {
                newDate = splitDate[0]+"."+splitDate[1]+"."+splitDate[2]+" "+splitDate[3]+":00";
            }
            else if(dateMonthYear.test(date)) {
                newDate = splitDate[0]+"."+splitDate[1]+"."+splitDate[2]+" 12:00";
            }
            else if(dateMonthHourMin.test(date)) {
                newDate = splitDate[0]+"."+splitDate[1]+"."+year+" "+splitDate[2]+":"+splitDate[3];
            }
            else if(dateMonthHour.test(date)) {
                newDate = splitDate[0]+"."+splitDate[1]+"."+year+" "+splitDate[2]+":00";
            }
            else if(dateMonth.test(date)) {
                newDate = splitDate[0]+"."+splitDate[1]+"."+year+" 12:00";
            }
            else if(dateHourMin.test(date)) {
                newDate = splitDate[0]+"."+month+"."+year+" "+splitDate[1]+":"+splitDate[2];
            }
            else if(dateHour.test(date)) {
                newDate = splitDate[0]+"."+month+"."+year+" "+splitDate[1]+":00";
            }
            else if(day.test(date)) {
                newDate = splitDate[0]+"."+month+"."+year+" 12:00";
            }
            return newDate;
        }

Answer 1

The problem you described is tackled by Natural Language Processing , Programming/Query Language Design fields.

One of the approaches for solving those kind of problems is manually written scanner using RegExp/other string scanning and working with the result the way you did. It works for simple languages, doesn't require much knowledge in language design department and usually is intuitive to modify.

If you however have feeling that input is going to grow to something more complicated I recommend replacing RegExp scanning with full-fledged parser/lexer using for example Jison "Your friendly JavaScript parser generator!" or anything else that suits you.

Answer 2

I believe you can consolidate some of your regular expressions and make this more compact.

The first thing I notice is that whitespace appears to be an important separator in your input strings. Specifically, the date (or day) is always separated from the hour/minute with a space. So the first thing I would do is split your input on a space:

var parts = date.split( /\s/ );
var datePart = parts[0];
var timePart = parts[1];     // could be undefined

Now we can process the date part and the time part (if it exists) separately. The components of your date part are always separated by a slash, a dash, a comma, or a period, so again we can just split it:

parts = datePart.split( /[\/\-\,\.]/ );
var day = parts[0];
var month = parts[1]  // could be undefined
var year = parts[2];  // could be undefined

You can split the time similarly, since hours and minutes are always separated by a colon:

if( timePart ) {
    parts = timePart.split( /:/ );
    var hour = parts[0];
    var minute = parts[1];   // could be undefined
}

This should make this a little more compact and easy to read and maintain. You could go even more compact with a singular regular expression with groups, but I feel that this approach would be better.