在javascript中删除除字符串的特定部分之外的所有部分

Question

I am writing a little app for Sharepoint. I am trying to extract some text from the middle of a field that is returned:

var ows_MetaInfo="1;#Subject:SW|NameOfADocument
vti_parservers:SR|23.0.0.6421
ContentTypeID:SW|0x0101001DB26Cf25E4F31488B7333256A77D2CA
vti_cachedtitle:SR|NameOfADocument
vti_title:SR|ATitleOfADocument
_Author:SW:|TheNameOfOurCompany
_Category:SW|
ContentType:SW|Document
vti_author::SR|mrwienerdog
_Comments:SW|This is very much the string I need extracted
vti_categories:VW|
vtiapprovallevel:SR|
vti_modifiedby:SR|mrwienerdog
vti_assignedto:SR|
Keywords:SW|Project Name
ContentType _Comments"

So......All I want returned is "This is very much the string I need extracted"

Do I need a regex and a string replace? How would you write the regex?

Answer 1

Yes, you can use a regular expression for this (this is the sort of thing they are good for). Assuming you always want the string after the pipe (|) on the line starting with "_Comments:SW|", here's how you can extract it:

var matchresult = ows_MetaInfo.match(/^_Comments:SW\|(.*)$/m);
var comment = (matchresult==null) ? "" : matchresult[1];

Note that the .match() method of the String object returns an array. The first (index 0) element will be the entire match (here, we the entire match is the whole line, as we anchored it with ^ and $; note that adding the "m" after the regex makes this a multiline regex, allowing us to match the start and end of any line within the multi-line input), and the rest of the array are the submatches that we capture using parenthesis. Above we've captured the part of the line that you want, so that will present in the second item in the array (index 1).

If there is no match ("_Comments:SW|" doesnt appear in ows_MetaInfo), then .match() will return null, which is why we test it before pulling out the comment.

If you need to adjust the regex for other scenarios, have a look at the Regex docs on Mozilla Dev Network: https://developer.mozilla.org/en/JavaScript/Guide/Regular_Expressions

Answer 2

You can use this code:

var match = ows_MetaInfo.match(/_Comments:SW\|([^\n]+)/);
if (match)
   document.writeln(match[1]);

Answer 3

I'm far from competent with RegEx, so here is my RegEx-less solution. See comments for further detail.

var extractedText = ExtractText(ows_MetaInfo);

function ExtractText(arg) {
    // Use the pipe delimiter to turn the string into an array
    var aryValues = ows_MetaInfo.split("|");

    // Find the portion of the array that contains "vti_categories:VW"
    for (var i = 0; i < aryValues.length; i++) {
        if (aryValues[i].search("vti_categories:VW") != -1)
            return aryValues[i].replace("vti_categories:VW", "");
    }

    return null;
}​

Here's a working fiddle to demonstrate .