在项目中，我们也许会在某些情况下对版本号进行检查、比较等操作。比如一个典型案例，在服务端判断APP客户端是否需要升级。

semver 就是专门用于语义化版本号检查的库，其也是语义化版本标准的制定者。

概念

semver 定义了两种概念： 

• 版本是指例如 0.4.1、1.2.7、1.2.4-beta.0 这样表示包的特定版本的字符串。 
• 范围则是对满足特定规则的版本的一种表示，例如 1.2.3-2.3.4、1.x、^0.2、>1.4

在这两种概念上可以进行很多种计算，例如比较两个版本的大小、判断一个版本是否满足一个范围、判断一个版本是否比范围中的任何版本都大等。

安装

npm install semver

用法

const semver = require('semver')

semver.valid('1.2.3') // '1.2.3'
semver.valid('a.b.c') // null
semver.clean('  =v1.2.3   ') // '1.2.3'
semver.satisfies('1.2.3', '1.x || >=2.5.0 || 5.0.0 - 7.2.3') // true
semver.gt('1.2.3', '9.8.7') // false
semver.lt('1.2.3', '9.8.7') // true

命令行

$ semver -h

A JavaScript implementation of the https://semver.org/ specification
Copyright Isaac Z. Schlueter

Usage: semver [options] <version> [<version> [...]]
Prints valid versions sorted by SemVer precedence

Options:
-r --range <range>
        Print versions that match the specified range.

-i --increment [<level>]
        Increment a version by the specified level.  Level can
        be one of: major, minor, patch, premajor, preminor,
        prepatch, or prerelease.  Default level is 'patch'.
        Only one version may be specified.

--preid <identifier>
        Identifier to be used to prefix premajor, preminor,
        prepatch or prerelease version increments.

-l --loose
        Interpret versions and ranges loosely

-p --include-prerelease
        Always include prerelease versions in range matching

-c --coerce
        Coerce a string into SemVer if possible
        (does not imply --loose)

--rtl
        Coerce version strings right to left

--ltr
        Coerce version strings left to right (default)

Program exits successfully if any valid version satisfies
all supplied ranges, and prints all satisfying versions.

If no satisfying versions are found, then exits failure.

Versions are printed in ascending order, so supplying
multiple versions to the utility will just sort them.

链接: https://fly63.com/nav/3823