eval() on string replacement | JavaScript

Question

Is it possible that an array of string replacements using regex can use eval to execute and return a value from a function which I need to be done via this method:

var message = $('#message').html();

var searchstring = [
    /<span style="color: rgb((.*), (.*), (.*));">(.*)<\/span>/gi,
    // other regex
];

var replacestring = [
    eval('RGBtoHex($1, $2, $3)'),
    // other regex
];

for(i = 0; i < searchstring.length; i++)
{
    message = message.replace(searchstring[i], replacestring[i]);
}

$('.message-box').val(message);

I'm trying to convert RGB to a hexadecimal value so it should change to something like: rgb(255, 255, 255) to #FFFFFF. However, when I do this it says in Firebug: $1 is not defined which is located for this: eval('RGBtoHex($1, $2, $3)'),.

How will I be able to execute an eval() function to return rgb to a hexadecimal value while doing string replacements with .replace()?

Everything works perfectly except the eval part.

Zsolt Meszaros · Accepted Answer · 2021-01-26 11:22:33Z

6

It doesn't work like that. When you call eval, you are evaling the raw string 'RGBtoHex($1, $2, $3)'.

You need to pass a function to replace:

message.replace(
    /rgb\((\d+), (\d+), (\d+)\)/gi, 
    function(str, r, g, b) { return RGBtoHEX(r, g, b); }
);

edited Jan 26, 2021 at 11:22

Zsolt Meszaros

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answered Dec 30, 2010 at 21:15

SLaks

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4 Comments

MacMac Over a year ago

Ah, thanks for that. I've certainly gave a read on that documentation. Thanks! :) will vote in 3 minutes

Olga Over a year ago

I am a bit curious as to your example, where do str, r, g, b com from? I mean say I have this code

var templateString = '<div class="slide" style="background-image:url(|@imageURL|); width:|@width|px;" ></div>';  var regex = /\|@([a-zA-z1-9_]*)\|/g; var imageURL = 'someImage.jpg'; var width = 500;  var replaceString = templateString.replace(regex, '$1')

can I somehow eval $1 to get the imageURL value and width value?

Olga Over a year ago

Oh I worked it out=) Still looks like magic but

var replaceString = templateString.replace(regex,                                             function(x, y)                                            { console.log(x); console.log(y); var value = eval(y); return value;}                                              );

is exactly what I needed

SLaks Over a year ago

@Olga: See the documentation: developer.mozilla.org/en/JavaScript/Reference/Global_Objects/… The callback takes parameters

6502 · Accepted Answer · 2010-12-30 21:17:39Z

0

Your eval is executed during the creation of the replacement array. Sure you can call code at replacement time by simply passing a function accepting a parameter instead of a substitute string... for example

"1234".replace(/\d/g,function(x){return parseInt(x)+1})

returns "2345" as result

answered Dec 30, 2010 at 21:17

6502

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