Replace multiple occurence string using array element

Question

I have several strings in an associative array:

 var arr = {
 '============================================': '---------',
 '++++++++++++++++++++++++++++++++++++++++++++': '---------',
 '--------------------------------------------': '---------'
 };

I want to replace occurrences of each key with the corresponding value. What I've come up with is:

 for (var i in arr)
 {
 strX = str.replace(i, arr[i]);
 console.log('arr[\''+i+'\'] is ' + arr[i] + ': ' + strX);
 }

This works, but only on first occurence. If I change the regex to /i/g, the code doesn't work.

for (var i in arr)
{
 strX = str.replace(/i/g, arr[i]);
 console.log('arr[\''+i+'\'] is ' + arr[i] + ': ' + strX);
}

Do you guys know how to work around this?

• cdhowie: Don't use for ... in on arrays. As soon as someone touches the array prototype you will be in for a world of hurt.
• Bakudan: I don`t want to be evil but array is [], and {} is object.
• user113716: @cdhowie: OP isn't actually using an Array. var arr = {...}.
• cdhowie: This is true. The name arr confused me. :) Still, if someone touches the object prototype, the OP will still have issues.
• LoveAndCoding: Touching the object prototype has a lot of its own issues though, and if I remember correctly, can't be done in IE at all.

Answer 1

Instead of

strX = str.replace(/i/g, arr[i]);

you want to do something like.

strX = str.replace(new RegExp(i, "g"), arr[i]);

This is because /i/g refers to the letter i, not the value of variable i. HOWEVER one of your base string has plus signs, which is a metacharacter in regexes. These have to be escaped. The quickest hack is as follows:

new RegExp(i.replace(/\+/g, "\\+"), "g"), arr[i]);

Here is a working example: http://jsfiddle.net/mFj2f/

In general, though, one should check for all the metacharacters, I think.

• user113716: There'll actually be an issue with the '++++++++' one since + needs to be escaped.
• user166390: Sadly there is no builtin way to escape special regex chars :(
• Ray Toal: Darn, no \Q, \E or Pattern.quote, r'...' or %r{...} in JS.... I'm still looking, though. I'll find something for the OP unless someone beats me to it. :-)
• user113716: I think you may need to do an .indexOf() test for +, then do a .replace(/\+/g,'\\+').
• Ray Toal: Thanks for the commentary, pst and patrick. I was a little confused why the fiddle was not working at first! +1 to patrick and pst.

Answer 2

The i in the regex will be the string i, not the variable i. Try instead new RegExp(i,'g'); and you should get the desired results

Answer 3

 var W,H,A,K;
W='123456'.split(''),
H='test this WHAK com www for'.split(' '),
A='2 is a 1 (1ed 6 3 2, 1 6 3 that), 1ing 6 5.3.4';
K=0;for(K in W)A=A.split(W[K]).join(H[K]);
 document.write(A);

• HaveNoDisplayName: add explanation to your answer?
• Dave Brown: 1sr line declares variables. Lines 2 and 3 are arrays of same number of search replacements. 4th line is the map to our original code. Then search and replace is done by splitting by search word and join by replacement word/phrase. Once replacing is done, the code is run by eval.