1、pkg-dir

'use strict';
const path = require('path');
const findUp = require('find-up');
const pkgDir = async cwd => {
    const filePath = await findUp('package.json', {cwd});
    return filePath && path.dirname(filePath);
};
module.exports = pkgDir;
// TODO: Remove this for the next major release
module.exports.default = pkgDir;
module.exports.sync = cwd => {
    //该库用于在某个目录下向上找指定文件,找到返回该文件路径，找不到返回null
    //接收两个参数 第一要寻找的文件，第二个 路径
    const filePath = findUp.sync('package.json', {cwd});
    return filePath && path.dirname(filePath);
};

2、find-up

'use strict';
const path = require('path');
const locatePath = require('locate-path');
const pathExists = require('path-exists');
const stop = Symbol('findUp.stop');
module.exports = async (name, options = {}) => {
    let directory = path.resolve(options.cwd || '');
    const {root} = path.parse(directory);
    const paths = [].concat(name);
    const runMatcher = async locateOptions => {
        if (typeof name !== 'function') {
            return locatePath(paths, locateOptions);
        }
        const foundPath = await name(locateOptions.cwd);
        if (typeof foundPath === 'string') {
            return locatePath([foundPath], locateOptions);
        }
        return foundPath;
    };
    // eslint-disable-next-line no-constant-condition
    while (true) {
        // eslint-disable-next-line no-await-in-loop
        const foundPath = await runMatcher({...options, cwd: directory});
        if (foundPath === stop) {
            return;
        }
        if (foundPath) {
            return path.resolve(directory, foundPath);
        }
        if (directory === root) {
            return;
        }
        directory = path.dirname(directory);
    }
};
module.exports.sync = (name, options = {}) => {
    let directory = path.resolve(options.cwd || '');
    const {root} = path.parse(directory);
    const paths = [].concat(name);
    //运行匹配器
    const runMatcher = locateOptions => {
        if (typeof name !== 'function') {
            //当前库的作用就是判断某个文件名称(带后缀)数组中是否有一个文件是否在某个目录下，
            //如果在，则返回这个文件名称(带后缀)，如果不在则返回undefined
            return locatePath.sync(paths, locateOptions);
        }
        const _l=locateOptions
        const foundPath = name(locateOptions.cwd);
        if (typeof foundPath === 'string') {
            return locatePath.sync([foundPath], locateOptions);
        }
        return foundPath;
    };
    // eslint-disable-next-line no-constant-condition
    while (true) {
        const foundPath = runMatcher({...options, cwd: directory});
        if (foundPath === stop) {
            return;
        }
        if (foundPath) {
            //如果foundPath存在，返回相对路径
            return path.resolve(directory, foundPath);
        }
        if (directory === root) {
            return;
        }
        directory = path.dirname(directory);
    }
};
module.exports.exists = pathExists;
module.exports.sync.exists = pathExists.sync;
module.exports.stop = stop;