string = string.replace(/[&\/\\#,+()$~%.'":*?<>{}]/g,'_');

Alternatively, to change all characters except numbers and letters, try:

string = string.replace(/[^a-zA-Z0-9]/g,'_');

The ) character in regular expressions is a special character. You'll have to escape it:

str = str.replace(/\)/g,"%29")

You should use the string replace function, with a single regex. Assuming by special characters, you mean anything that's not letter, here is a solution:

const str = "abc's test#s";
console.log(str.replace(/[^a-zA-Z ]/g, ""));

You can use character class with ^ negation:

this.value = this.value.replace(/[^a-zA-Z0-9_-]/g,'');

Tests:

console.log('Abc054_34-bd'.replace(/[^a-zA-Z0-9_-]/g,'')); // Abc054_34-bd
console.log('Fš 04//4.'.replace(/[^a-zA-Z0-9_-]/g,'')); // F044

So by putting characters in [^...], you can decide which characters should be allowed and all others replaced.

Sure is!

Running this in the Firebug console

"®ü".replace(/[®ü]/g,"replaced")

returned

"replacedreplaced"

You can also do

"®ü".replace(/[\xAE\xFC]/g,"Wohoo! ");

which returns

"Wohoo! Wohoo! "

A good hex symbol lookup page can be found at http://www.ascii.cl/htmlcodes.htm

Example

running this jQuery on this page

$(".post-text").text().replace(/®/g," ******** ")

returns

" is it possible to translate special characters like ******** , ü etc with javascript 
String replace function? Use this syntax... string.replace(/\xCC/g/,''); Where 'CC' is 
the hex character code for the char you are wanting to replace. In this example I am 
replacing with empty string ''. yes, and is as simple as can be: ' ******** '.replace('
 ******** ','anything'); Sure is! Running this in the Firebug console " ******** ü".
replace(/[ ******** ü]/g,"replaced") returned replacedreplaced "

You can:

str = str.replace(/\[(:[a-z]*)\]/g, "<!--$1-->");