regex variable

[Old Pedant]

It's not clear at all to me what your reason for using eval( ) is.

Is it simply so you can do it all in one line?

Not a good reason.

What's the difference between:

    replace(eval("/"+var1+"/gi"), anything)

and

    replace( (new RegExp( var1, "gi" ) ), anything )

???
Surely the second version is much more efficient, by avoiding the eval( ).

Even if eval( ) isn't evil, it's certainly less efficient than most anything else. (Especially in MSIE, unsurprisingly.)

[rdspoons]

Old Pendant,

I've evaluated your comment and of course you're right. Thank you. I do fall back to eval when I believe it's required, but in the examples posted here I used eval because its a legal (if unwelcome) option that provided a solution. There is no doubt that replace((new RegExp(var1,"gi")),var2) is superior and more desirable, and as such, I stand corrected - in my evaluations.

[Old Pedant]

I'd be really interested to see a situation where eval() is *REQUIRED*.

Other than parsing JSON that is returned by an AJAX call or something very similar.

I have yet to find a case where it is required, except when processing external JS data input.

[007julien]

I forgott the / which is also to escape with javascript !

String.prototype.toRegExp=function(){return this.replace(/\\/g,'\\\\').replace(/(\[|\^|\$|\.|\||\?|\*|\+|\(|\)|\/)/g,'\\$1')}

//Example of use with all the «meta»characters
var something="[\\^$.|?*+()/"; // the slashe is to escape
	
alert(("foo"+something+"bar").replace(new RegExp(something.toRegExp(),'g'),''));// =>'foobar'