Due to a bug in npm v7, Currently, node.js v16.x should be used for evaluation purposes.

[nxhack]

Ref: npm/cli#2339
Ref: npm/cli#3175
Ref: npm/cli#3192

Ref: npm/cli#2900
Ref: npm/cli#1969
Ref: npm/cli#2921

[nxhack]

There are some breaking changes in npm v7. There are also probably quite a few bugs.
To get around this, I decided to downgrade npm to v6.

[nxhack]

The npm v7 support is now in the master branch, and the way to create node modules has been significantly changed. I haven't tested everything yet, so please report any problems.

d686699

[nxhack]

With node v16.2.0, npm is now v7.13.0.
I'll adjust with npm v7 from now on.