Contrary to misinformation provided above, regular expressions are extremely efficient. The caveat is that, when possible, they should be in a position so that they are compiled exactly once in the life of the program.
Here is a solution that gives both dirname and basename.
const rx1 = /(.*)\/+([^/]*)$/; // (dir/) (optional_file)
const rx2 = /()(.*)$/; // () (file)
function dir_and_file(path) {
// result is array with
// [0] original string
// [1] dirname
// [2] filename
return rx1.exec(path) || rx2.exec(path);
}
// Single purpose versions.
function dirname(path) {
return (rx1.exec(path) || rx2.exec(path))[1];
}
function basename(path) {
return (rx1.exec(path) || rx2.exec(path))[2];
}
As for performance, I have not measured it, but I expect this solution to be in the same range as the fastest of the others on this page, but this solution does more. Helping the real-world performance is the fact that rx1 will match most actual paths, so rx2 is rarely executed.
Here is some test code.
function show_dir(parts) {
console.log("Original str :"+parts[0]);
console.log("Directory nm :"+parts[1]);
console.log("File nm :"+parts[2]);
console.log();
}
show_dir(dir_and_file('/absolute_dir/file.txt'));
show_dir(dir_and_file('relative_dir////file.txt'));
show_dir(dir_and_file('dir_no_file/'));
show_dir(dir_and_file('just_one_word'));
show_dir(dir_and_file('')); // empty string
show_dir(dir_and_file(null));
And here is what the test code yields:
# Original str :/absolute_dir/file.txt
# Directory nm :/absolute_dir
# File nm :file.txt
#
# Original str :relative_dir////file.txt
# Directory nm :relative_dir
# File nm :file.txt
#
# Original str :dir_no_file/
# Directory nm :dir_no_file
# File nm :
#
# Original str :just_one_word
# Directory nm :
# File nm :just_one_word
#
# Original str :
# Directory nm :
# File nm :
#
# Original str :null
# Directory nm :
# File nm :null
By the way, "node" has a built in module called "path" that has "dirname" and "basename". Node's "path.dirname()" function accurately imitates the behavior of the "bash" shell's "dirname," but is that good? Here's what it does:
- Produces
'.' (dot) when path=="" (empty string).
- Produces
'.' (dot) when path=="just_one_word".
- Produces
'.' (dot) when path=="dir_no_file/".
I prefer the results of the function defined above.
