如何查找给定路径是绝对/相对路径还是将其转换为绝对路径以进行文件操作？

Question

I am writing a small windows script in javascript/jscript for finding a match for a regexp with a string that i got by manipulating a file.

The file path can be provided relative or absolute. How to find whether a given path is absolute/relative and convert it to absolute for file manipulation?

Answer 1

How to find whether a given path is absolute/relative ...

From the MSDN article Naming Files, Paths, and Namespaces :

A file name is relative to the current directory if it does not begin with one of the following:

• A UNC name of any format, which always start with two backslash characters ("\\\\"). For more information, see the next section.
• A disk designator with a backslash, for example "C:\\" or "d:\\".
• A single backslash, for example, "\\directory" or "\\file.txt". This is also referred to as an absolute path .

So, strictly speaking, an absolute path is the one that begins with a single backslash ( \\ ). You can check this condition as follows:

if (/^\\(?!\\)/.test(path)) {
  // path is absolute
}
else {
  // path isn't absolute
}

But often by an absolute path we actually mean a fully qualified path . In this is the case, you need to check all three conditions in order to distinguish between full and relative paths. For example, your code could look like this:

function pathIsAbsolute(path)
{
  if ( /^[A-Za-z]:\\/.test(path) ) return true;
  if ( path.indexOf("\\") == 0 )   return true;
  return false;
}

or (using a single regex and a bit less readable):

function pathIsAbsolute(path)
{
  return /^(?:[A-Za-z]:)?\\/.test(path);
}

---

... and convert it to absolute for file manipulation?

Use the FileSystemObject.GetAbsolutePathName method:

var fso = new ActiveXObject("Scripting.FileSystemObject");
var full_path = fso.GetAbsolutePathName(path);

Answer 2

To check whether the path is relative or absolute, look for a leading / . If it doesn't have one, you need to concatenate the path to a base path. Some programming environments have a "current working directory", but Javascript that lives in the browser doesn't, so you just need to pick a base path and stick to it.

function full_path(my_path) {
    var base_path = "/home/Sriram/htdocs/media";
    var path_regex = /^\/.*$/;
    if(path_regex.test(my_path)) {
        return my_path;
    } else {
        return base_path + my_path;
    }
}

Paths can contain newlines, which the javascript regex . won't match, so you might want to develop a more sophisticated regex to make sure all paths will work properly. However, I'd consider that outside the scope of this answer, and of my knowledge. :-)