Friday, May 25, 2012

JavaScript: string contains


How can I check if one string contains another substring in JavaScript?



Usually I would expect a String.contains() method, but there doesn't seem to be one.



Edit: thanks for all the answers :) However, it seems that I have another problem :(



When I use the ".indexof" method, Firefox refuses to start the JavaScript code (this is for an extension).



My code is: 





var allLinks = content.document.getElementsByTagName("a");



for (var i=0, il=allLinks.length; i<il; i++) {

    elm = allLinks[i];

    var test = elm.getAttribute("class");

    if (test.indexof("title") !=-1) {

        alert(elm);

        foundLinks++;

    }

}



if (foundLinks === 0) {

    alert("No title class found");

} 

else {

    alert("Found " + foundLinks + " title class");

}


Firefox doesn't display an alert box. This works if I get rid of the .indexof() method. I already tried something like if (test=="title")... , but it didn't work.


Source: Tips4all
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9 comments:

  1. UserMay 25, 2012 at 6:24 AM

    var s = "foo";
    alert(s.indexOf("oo") != -1);


    indexOf returns the position of the string in the other string. If not found, it will return -1.

    https://developer.mozilla.org/en/Core%5FJavaScript%5F1.5%5FReference/Objects/String/indexOf

    ReplyDelete
  2. UserMay 25, 2012 at 6:24 AM

    I know your question is already answered, but I thought this might be helpful too.

    You can easily add a contains method to String with this statement:

    String.prototype.contains = function(it) { return this.indexOf(it) != -1; };


    Note: see the comments below for a valid argument for not using this. My advice: use your own judgement.

    ReplyDelete
  3. UserMay 25, 2012 at 6:24 AM

    The problem with your code is that Javascript is case sensitive. Your method call

    indexof()


    should actually be

    indexOf()


    Try fixing it and see if that helps:

    if (test.indexOf("title") !=-1) {
    alert(elm);
    foundLinks++;
    }

    ReplyDelete
  4. UserMay 25, 2012 at 6:24 AM

    You could use the JavaScript search() method.

    Syntax is: string.search(regexp)

    It returns the position of the match, or -1 if no match is found.

    See examples there: jsref_search

    You don't need a complicated regular expression syntax. If you are not familiar with them a simple st.search("title") will do. If you want your test to be case insensitive, then you should do st.search(/title/i).

    ReplyDelete
  5. UserMay 25, 2012 at 6:24 AM

    var index = haystack.indexOf(needle);

    ReplyDelete
  6. UserMay 25, 2012 at 6:24 AM

    You can use jQuery's ':contains' selector.

    $("div:contains('John')")


    check it here: http://api.jquery.com/contains-selector/

    ReplyDelete
  7. UserMay 25, 2012 at 6:24 AM

    You need to call indexOf with a capital "O" as mentioned. It should also be noted, that in JavaScript class is a reserved word, you need to use className to get this data attribute. The reason it's probably failing is because it's returning a null value. You can do the following to get your class value...

    var test = elm.getAttribute("className");
    //or
    var test = elm.className

    ReplyDelete
  8. UserMay 25, 2012 at 6:24 AM

    This just worked for me. It selects for strings that do not contain the term "Deleted:"

    if (eventString.indexOf("Deleted:") == -1)

    ReplyDelete
  9. UserMay 25, 2012 at 6:24 AM

    Use regular expression

    RegExp.test(string)

    ReplyDelete

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