[javascript] How to extract a string using JavaScript Regex?

I'm trying to extract a substring from a file with JavaScript Regex. Here is a slice from the file :

DATE:20091201T220000
SUMMARY:Dad's birthday

the field I want to extract is "Summary". Here is the approach:

extractSummary : function(iCalContent) {
  /*
  input : iCal file content
  return : Event summary
  */
  var arr = iCalContent.match(/^SUMMARY\:(.)*$/g);
  return(arr);
}

Your regular expression most likely wants to be

/\nSUMMARY:(.*)$/g

A helpful little trick I like to use is to default assign on match with an array.

var arr = iCalContent.match(/\nSUMMARY:(.*)$/g) || [""]; //could also use null for empty value
return arr[0];

This way you don't get annoying type errors when you go to use arr

(.*) instead of (.)* would be a start. The latter will only capture the last character on the line.

Also, no need to escape the :.

this is how you can parse iCal files with javascript

    function calParse(str) {

        function parse() {
            var obj = {};
            while(str.length) {
                var p = str.shift().split(":");
                var k = p.shift(), p = p.join();
                switch(k) {
                    case "BEGIN":
                        obj[p] = parse();
                        break;
                    case "END":
                        return obj;
                    default:
                        obj[k] = p;
                }
            }
            return obj;
        }
        str = str.replace(/\n /g, " ").split("\n");
        return parse().VCALENDAR;
    }

    example = 
    'BEGIN:VCALENDAR\n'+
    'VERSION:2.0\n'+
    'PRODID:-//hacksw/handcal//NONSGML v1.0//EN\n'+
    'BEGIN:VEVENT\n'+
    'DTSTART:19970714T170000Z\n'+
    'DTEND:19970715T035959Z\n'+
    'SUMMARY:Bastille Day Party\n'+
    'END:VEVENT\n'+
    'END:VCALENDAR\n'


    cal = calParse(example);
    alert(cal.VEVENT.SUMMARY);

This code works:

  let str = "governance[string_i_want]"; 
  let res = str.match(/[^governance\[](.*)[^\]]/g);

res will equal "string_i_want". However, in this example res is still an array, so do not treat res like a string.

By grouping the characters I do not want, using [^string], and matching on what is between the brackets, the code extracts the string I want!

You can try it out here: https://www.w3schools.com/jsref/tryit.asp?filename=tryjsref_match_regexp

Good luck.

function extractSummary(iCalContent) {
  var rx = /\nSUMMARY:(.*)\n/g;
  var arr = rx.exec(iCalContent);
  return arr[1]; 
}

You need these changes:

• Put the * inside the parenthesis as suggested above. Otherwise your matching group will contain only one character.

• Get rid of the ^ and $. With the global option they match on start and end of the full string, rather than on start and end of lines. Match on explicit newlines instead.

• I suppose you want the matching group (what's inside the parenthesis) rather than the full array? arr[0] is the full match ("\nSUMMARY:...") and the next indexes contain the group matches.

• String.match(regexp) is supposed to return an array with the matches. In my browser it doesn't (Safari on Mac returns only the full match, not the groups), but Regexp.exec(string) works.