path.resolve源码实现（简单版）

//解析文件路径。类似于path.resolve

　　resolve(...paths){

        let resolvePath = '';

        let isAbsolutePath = false;

        for(let i = paths.length-1; i > -1; i--){

            let path = paths[i];

            if(isAbsolutePath){

                break;

            }

            if(!path){

                continue

            }

            resolvePath = path + '/' + resolvePath;

            isAbsolutePath = path.charCodeAt(0) === 47;

        }

        if(/^\/+$/.test(resolvePath)){

            resolvePath = resolvePath.replace(/(\/+)/,'/')

        }else{

            resolvePath = resolvePath.replace(/(?!^)\w+\/+\.{2}\//g, '')

            .replace(/(?!^)\.\//g,'')

            .replace(/\/+$/, '')

        }

        return resolvePath;

    }

console.log(resolve('/aa','../bb','cc','dd'))

console.log(resolve('/aa','../bb','./cc','dd'))

console.log(resolve('/','/system','user','userIndex'))