优化

‘liusuyi’

2023-10-21 ae92b6823499cfab77201b4033922fa373fb37a3

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module.exports = function normalize(path) {
    var parts = path.split(/(\\+|\/+)/);
    if(parts.length === 1)
        return path;
    var result = [];
    var absolutePathStart = 0;
    for(var i = 0, sep = false; i < parts.length; i++, sep = !sep) {
        var part = parts[i];
        if(i === 0 && /^([A-Z]:)?$/i.test(part)) {
            result.push(part);
            absolutePathStart = 2;
        } else if(sep) {
            result.push(part[0]);
        } else if(part === "..") {
            switch(result.length) {
                case 0:
                    // i. e. ".." => ".."
                    // i. e. "../a/b/c" => "../a/b/c"
                    result.push(part);
                    break;
                case 2:
                    // i. e. "a/.." => ""
                    // i. e. "/.." => "/"
                    // i. e. "C:\.." => "C:\"
                    // i. e. "a/../b/c" => "b/c"
                    // i. e. "/../b/c" => "/b/c"
                    // i. e. "C:\..\a\b\c" => "C:\a\b\c"
                    i++;
                    sep = !sep;
                    result.length = absolutePathStart;
                    break;
                case 4:
                    // i. e. "a/b/.." => "a"
                    // i. e. "/a/.." => "/"
                    // i. e. "C:\a\.." => "C:\"
                    // i. e. "/a/../b/c" => "/b/c"
                    if(absolutePathStart === 0) {
                        result.length -= 3;
                    } else {
                        i++;
                        sep = !sep;
                        result.length = 2;
                    }
                    break;
                default:
                    // i. e. "/a/b/.." => "/a"
                    // i. e. "/a/b/../c" => "/a/c"
                    result.length -= 3;
                    break;
            }
        } else if(part === ".") {
            switch(result.length) {
                case 0:
                    // i. e. "." => "."
                    // i. e. "./a/b/c" => "./a/b/c"
                    result.push(part);
                    break;
                case 2:
                    // i. e. "a/." => "a"
                    // i. e. "/." => "/"
                    // i. e. "C:\." => "C:\"
                    // i. e. "C:\.\a\b\c" => "C:\a\b\c"
                    if(absolutePathStart === 0) {
                        result.length--;
                    } else {
                        i++;
                        sep = !sep;
                    }
                    break;
                default:
                    // i. e. "a/b/." => "a/b"
                    // i. e. "/a/." => "/"
                    // i. e. "C:\a\." => "C:\"
                    // i. e. "a/./b/c" => "a/b/c"
                    // i. e. "/a/./b/c" => "/a/b/c"
                    result.length--;
                    break;
            }
        } else if(part) {
            result.push(part);
        }
    }
    if(result.length === 1 && /^[A-Za-z]:$/.test(result))
        return result[0] + "\\";
    return result.join("");
};