Reference syntax does not match behavior for replace()

The function below does not work unless I assume that .replace returns the new string. The syntax implies that the input string itself it modified.

MDN

str.replace(regexp|substr, newSubStr|function[, Non-standardflags]);

Code

escape: function ( second_split )

{

    for( element in second_split )

    {

    second_split[element] = second_split[element].replace('**', '*');

    second_split[element] = second_split[element].replace('*|', '|');

    }

return second_split;

},