Imagine you end up with double dashes, and want to replace them with a single character and not doubles of the replace character. You can just use array split and array filter and array join.
var str = "This-is---a--news-----item----";
Then to replace all dashes with single spaces, you could do this:
var newStr = str.split('-').filter(function(item) {
item = item ? item.replace(/-/g, ''): item
return item;
}).join(' ');
Now if the string contains double dashes, like '----' then array split will produce an element with 3 dashes in it (because it split on the first dash). So by using this line:
item = item ? item.replace(/-/g, ''): item
The filter method removes those extra dashes so the element will be ignored on the filter iteration. The above line also accounts for if item is already an empty element so it doesn't crash on item.replace.
Then when your string join runs on the filtered elements, you end up with this output:
"This is a news item"
Now if you were using something like knockout.js where you can have computer observables. You could create a computed observable to always calculate "newStr" when "str" changes so you'd always have a version of the string with no dashes even if you change the value of the original input string. Basically they are bound together. I'm sure other JS frameworks can do similar things.