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： https://github.com/nodejs/node/blob/master/lib/path.js

<div class="jb51code">
<pre class="brush:js;">
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);
}