JavaScript string replace() not working when replacing variable

Question

I'm trying to create a JavaScript script for highlighting certain text on a page. Right now I'm having issues trying to replace text (from the body html) with other text. I want to replace all instances of each item in the array highlights with some other text.

The code that I'm using is:

    var responseText = server.responseText;
    var highlights = responseText.split("\n");
    var text = document.body.innerHTML;

    for (i in highlights) {
        if (highlights[i].length > 1) {
            var exp = new RegExp(highlights[i], "g");
            console.log(exp);
            console.log(highlights[i]);
            text = text.replace(exp, "XXXXXXXXXXX");
        }
    }

    document.body.innerHTML = text;

Currently, I am getting the correct value printouts for highlights[i] and I think I am for the regular expression exp; if highlights[i] is 'Remember', then the printout I'm getting for exp is '/Remember/g' (without the quotation marks) -- but it's not replacing the word 'Remember' on the page. 'And if I replace highlights[i] in the new RegExp() with simply the string "Remember" it works correctly. Any ideas on what's wrong?

EDIT: I solved the problem! When creating the RegExp() I passed in highlights[i].trim() instead of just highlights[i] to get rid of whitespace at the beginning/end and it appears to be working now.

Don't use for ..in to iterate through arrays, use a regular for loop. — Musa
– Musa, Commented Sep 10, 2012 at 6:42
Can you reproduce this behaviour with a live demo? JS Fiddle, or similar? — David Thomas
– David Thomas, Commented Sep 10, 2012 at 6:52
@Musa What's wrong with for...in? Is there any reason why that would be messing up the replace()? — scaevity
– scaevity, Commented Sep 10, 2012 at 6:52
str.replace will replace only the first element of a string if you do not pass a regular 'Regular expression' :) — enesunal
– enesunal, Commented Sep 10, 2012 at 6:53

DhruvPathak · Accepted Answer · 2012-09-10 07:19:56Z

2

There is some problem with your multiline server.responseText . I replaced the input with spaces instead of newlines, and all the replacements work fine :

http://jsfiddle.net/XTdgJ/1/

answered Sep 10, 2012 at 7:19

DhruvPathak

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2 Comments

scaevity Over a year ago

Ok, so I called trim() on each line (to clean them up) before creating the regular expression and it appears to be working now. I thought that I'd already tried it earlier, but I guess not.

DhruvPathak Over a year ago

@scae newlines are usually hard to detect in console as well !

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