使用JavaScript实现node.js中的path.join方法

node.js中的 path.join 非常方便，能直接按相对或绝对合并路径，使用： path.join([path1], [path2], [...])，有时侯前端也需要这种方法，如何实现呢？

其实直接从 node.js 的 path.js 拿到源码加工一下就可以了：

1. 将 const 等 es6 属性改为 var，以便前端浏览器兼容
2. 添加一个判断路戏分隔符的变量 sep，即左斜杠还是右斜杠，以第一个路戏分隔符为准
3. 将引用的变量和函数放到一个文件里就可以了：

path 的源码：

var char_forward_slash = 47
var char_backward_slash = 92
var char_dot = 46
function ispathseparator(code) {
 return code === char_forward_slash || code === char_backward_slash;
}
function isposixpathseparator(code) {
 return code === char_forward_slash;
}
function normalize(path) {
 if (path.length === 0)
  return '.';
 var isabsolute = path.charcodeat(0) === char_forward_slash;
 var trailingseparator =
  path.charcodeat(path.length - 1) === char_forward_slash;
 // normalize the path
 path = normalizestring(path, !isabsolute, '/', isposixpathseparator);
 if (path.length === 0 && !isabsolute)
  path = '.';
 if (path.length > 0 && trailingseparator)
  path += '/';
 if (isabsolute)
  return '/' + path;
 return path;
}
function normalizestring(path, allowaboveroot, separator, ispathseparator) {
 var res = '';
 var lastsegmentlength = 0;
 var lastslash = -1;
 var dots = 0;
 var code;
 for (var i = 0; i <= path.length; ++i) {
  if (i < path.length)
   code = path.charcodeat(i);
  else if (ispathseparator(code))
   break;
  else
   code = char_forward_slash;
  if (ispathseparator(code)) {
   if (lastslash === i - 1 || dots === 1) {
    // noop
   } else if (lastslash !== i - 1 && dots === 2) {
    if (res.length < 2 || lastsegmentlength !== 2 ||
      res.charcodeat(res.length - 1) !== char_dot ||
      res.charcodeat(res.length - 2) !== char_dot) {
     if (res.length > 2) {
      const lastslashindex = res.lastindexof(separator);
      if (lastslashindex !== res.length - 1) {
       if (lastslashindex === -1) {
        res = '';
        lastsegmentlength = 0;
       } else {
        res = res.slice(0, lastslashindex);
        lastsegmentlength = res.length - 1 - res.lastindexof(separator);
       }
       lastslash = i;
       dots = 0;
       continue;
      }
     } else if (res.length === 2 || res.length === 1) {
      res = '';
      lastsegmentlength = 0;
      lastslash = i;
      dots = 0;
      continue;
     }
    }
    if (allowaboveroot) {
     if (res.length > 0)
      res += `${separator}..`;
     else
      res = '..';
     lastsegmentlength = 2;
    }
   } else {
    if (res.length > 0)
     res += separator + path.slice(lastslash + 1, i);
    else
     res = path.slice(lastslash + 1, i);
    lastsegmentlength = i - lastslash - 1;
   }
   lastslash = i;
   dots = 0;
  } else if (code === char_dot && dots !== -1) {
   ++dots;
  } else {
   dots = -1;
  }
 }
 return res;
}
function join() {
 if (arguments.length === 0)
  return '.';
 var sep = arguments[0].indexof('/') > -1 ? '/' : '\\'
 var joined;
 var firstpart;
 for (var i = 0; i < arguments.length; ++i) {
  var arg = arguments[i];
  if (arg.length > 0) {
   if (joined === undefined)
    joined = firstpart = arg;
   else
    joined += sep + arg;
  }
 }
 if (joined === undefined)
  return '.';
 var needsreplace = true;
 var slashcount = 0;
 if (ispathseparator(firstpart.charcodeat(0))) {
  ++slashcount;
  var firstlen = firstpart.length;
  if (firstlen > 1) {
   if (ispathseparator(firstpart.charcodeat(1))) {
    ++slashcount;
    if (firstlen > 2) {
     if (ispathseparator(firstpart.charcodeat(2)))
      ++slashcount;
     else {
      // we matched a unc path in the first part
      needsreplace = false;
     }
    }
   }
  }
 }
 if (needsreplace) {
  // find any more consecutive slashes we need to replace
  for (; slashcount < joined.length; ++slashcount) {
   if (!ispathseparator(joined.charcodeat(slashcount)))
    break;
  }
  // replace the slashes if needed
  if (slashcount >= 2)
   joined = sep + joined.slice(slashcount);
 }
 return normalize(joined);
}

使用：

join('../var/www', '../abc')
> "../var/abc"
join('../var/www', '\abc')
../var/www/abc

总结

以上所述是小编给大家介绍的使用javascript实现node.js中的path.join方法，希望对大家有所帮助，如果对大家有所帮助