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用JavaScript实现node.js中的path.join方法

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[前端(javascript) 所属分类 前端(javascript) | 发布者 店小二05 | 时间 2018 | 作者 红领巾 ] 0人收藏点击收藏
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

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

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tags: path,res,var,length,CHAR,else,code,joined,gt,lastSlash,return,charCodeAt,SLASH,isPathSeparator
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