add tag value package.json code example

Example 1: npm get package.json version

node -pe "require('./package.json')['version']"

Example 2: npm update package.json version field by code

# From 1.0.0 -> 1.0.1
npm version patch 

# From 1.0.1 -> 1.1.0
npm version minor

# From 1.1.0 -> 2.0.0
npm version major