如何遍历字符串并替换除最后一个以外的所有句点？

Question

Let's say I have a string like this:

var test = my.long.file.name.zip

I am getting the total number of periods in this string with javascript like so:

var dots = (test.match(/\./g) || []).length;

I would then like to replace all of the periods in the string with underscores if there is more than one period in the string.

   if(dots>"1"){   
     var newname = test.replace(/\./g, "_");
     console.log(newname);
    }

The problem is that this is replacing all of the periods. I would like to keep the last on intact. So what I would like the newname variable to read as would be:

my_long_file_name.zip

My guess is that I should use $.each() somehow to iterate over all except the last one to change the name. How should I do this?

Answer 1

You dont necessarily need a loop, you could do it with a more complex regex, which uses a positive lookahead

The regex /\\.(?=.*\\.)/g finds periods, but only where there is a subsequent period somewhere further along, which means the last one is not matched.

 window.onload = function(){ var input = "my.long.file.name.zip" var result = input.replace(/\\.(?=.*\\.)/g,'_') alert(result); } 

Answer 2

Consider splitting the string on '.' , then re-joining all but the last with '_' :

 var test = "my.long.file.name.zip"; parts = test.split('.'); var plen = parts.length; if (plen > 1) { test = parts.slice(0, plen - 1).join('_') + "." + parts[plen - 1]; } console.log(test); 

Answer 3

a lookahead group in regex will work:

 var test = 'my.long.file.name.zip'; var result = test.replace(/\\.(?=[^.]*\\.)/g, '_'); alert(result); 

this matches a dot followed by ('anything but dot' and another dot), replacing only what is outside the group

Answer 4

var test = 'my.long.file.name.zip';
var last_index = test.lastIndexOf('.');
var newname = test;

if (-1 !== last_index) {
  newname = test.replace(/\./g, '_');
  newname = newname.substring(0, last_index).concat('.', newname.substring(last_index + 1));
}

console.log(newname);