Replace keyword with a javascript expression

Question

I have a string like hey! <input/>, Welcome hey! <input/>, Welcome in a template.

I need to replace every <input/> with the a JS expression this.input .

eg:

//Input
"hey! <input/>, Welcome";

Output should be:    
"hey! " + this.input + ", Welcome";

I can do a replace on the string with " + this.input + " but the problem is what if <input/> at the start or the end?

What is the best way to handle this?

Edit:

I don't want the output to be a string. I want the output to be a valid JS expression.

Valid inputs:
1) "hey! <input/>, Welcome";
2) "<input/>, Welcome";
3) "Welcome <input/>"

Outputs:
1) "hey! " + this.input + ", Welcome";
2) this.input + ", Welcome";
3) "Welcome " + this.input;

Answer 1

As I wrote in comments above you can use:

var input = 'foo';
var str = "hey! <input/>, Welcome";
str = str.replace(/(.*?)<input\/>(.*)/, '$1' + this.input + '$2');

console.log(str);
//=> "hey! foo, Welcome"

Answer 2

"hey! <input/>, Welcome".replace(/<input\/>/, this.input);

EDIT:

John Reisig made a blog entry about making a minimal templating language parser in javascript. It's well written and may be a good starting point for your own templating language.