How to replace part of a string with another string?

Question

Here's what I'm trying to do. Honestly, I'm not even sure where to start.

var text1 = 'ThE foX iS brown',

        text2 = 'the fox is brown the fox is brown THE FOX IS BROWN',

        index = text2.toLowerCase().indexOf(text1.toLowerCase()),

        output = 'do something with substring?';

    alert(index);

The "text2" should be changed to: ThE foX iS brown the fox is brown THE FOX IS BROWN

    var text1 = 'ThE foX iS brown the FOX is BrO',

        text2 = 'the fox is brown the fox is brown THE FOX IS BROWN',

        index = text2.toLowerCase().indexOf(text1.toLowerCase()),

        output = 'do something with substring?';

    alert(index);

And in this case "text2" should be changed to: ThE foX iS brown the FOX is BrOwn THE FOX IS BROWN

I thought that maybe I should first try to find the "first" occurrence of the string "text1" within "text2" but it doesn't seem to work? And I thought after that I could use substring? Or maybe there's even an easier way to do this? I'm not sure. Any help would be really appreciated. Thank you.

According to downvotes, this seems like a dumb question. Sorry. — isuckatcoding, Jun 19 '13 at 20:47
it's not dumb, it just doesn't show much effort on your part. you mentioned a few ideas you had - why not try some of them then come back when you have a more specific question? — user428517, Jun 19 '13 at 20:51
You can't modify strings in place in Javascript. Functions like `toLowerCase()` return a new string. — Barmar, Jun 19 '13 at 20:51
Can the match for `text1` be somewhere other than the beginning of `text2`? — Barmar, Jun 19 '13 at 20:54
@Barmar No, should start from beginning. I tried `replace`, but that cut off the rest of the string? And in this code above, it does not return the index, it's only empty. — isuckatcoding, Jun 19 '13 at 21:00
possible duplicate of [javascript replacing strings](http://stackoverflow.com/questions/7769808/javascript-replacing-strings) — jball, Jun 20 '13 at 16:43

Nick Humrich · Accepted Answer · 2013-06-20T14:36:53.460

1

It seams like you are simply trying to replace the first part of the string with text1.

You can try this.

int text1Size = text1.length;
output = text1 + text2.substring(text1Size);

edited Jun 20 '13 at 14:36

answered Jun 19 '13 at 20:53

Nick Humrich

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Oh, that makes sense. Easier too, I like it. Thank you. btw, I had to change it to `text1.length`. :) – isuckatcoding Jun 19 '13 at 21:03
Plus I had to remove `-1`. :) Now it works perfectly! – isuckatcoding Jun 19 '13 at 21:07

Domenico De Felice · Answer 2 · 2013-06-24T05:56:19.540

What you are looking for is to replace the first occurrence of the substring text1 in text2 with text1, ignoring the case.

You can build a regular expression for that, using the "i"gnore-case flag.

Assuming you don't know the contents of text1, you have to escape some special characters interpreted by regular expressions. Once you have your regular expression you can use replace.

Here is an example:

// Function to escape Regular Expressions special characters.
// From: http://stackoverflow.com/questions/3115150/how-to-escape-regular-expression-special-characters-using-javascript
RegExp.escape = function(text) {
  return text.replace(/[-[\]{}()*+?.,\\^$|#\s]/g, "\\$&");
};

var text1 = 'ThE foX iS brown';
var text2 = 'the fox is brown the fox is brown THE FOX IS BROWN';

// Create the Regular Expression with the "i"gnore-case flag
var re = new RegExp(RegExp.escape(text1), "i");

var output = text2.replace(re, text1);
// output -> ThE foX iS brown the fox is brown THE FOX IS BROWN

And here is a working fiddle.

Wow, this looks good too! Thank you very much. I upvoted your answer! Thank you for the effort and explanation! — isuckatcoding, Jun 19 '13 at 21:13
This solution is more general and will work wherever `text1` appears, not only at the begin of the string. — Domenico De Felice, Jun 19 '13 at 21:17

How to replace part of a string with another string?

2 Answers2