chore: resolve linting rules | let & const (#281)

[sinclairzx81]

This PR fixes the linting warnings across the codebase to resolve issue #281. It replaces var for let and const where appropriate.

Note: The majority of the replacements were fairly straightforward, however I did spot a possibly undefined condition on line 621 with respect to the variable walk. You may wish to double check the additional ref check I've added on this code path.

Checklist

• run npm run test and npm run benchmark
• tests and/or benchmarks are included
• documentation is changed or added
• commit message and code follows the Developer's Certification of Origin
  and the Code of conduct

[RafaelGSS]

LGTM.

[Eomm]

Did you run the banchmark too?
Could you share the results?

[mcollina]

You should not replace for (var i with for (let i, it's slower in most cases in supported node versions.

[sinclairzx81]

@Eomm Hi, see below for comparative benchmarks using let | const vs var currently on the master branch. Results do vary a little from test to test, but seem about on par.

test machine

cpu  AMD Ryzen 7 3700X 8-Core Processor
ram  32GB 
node v12.18.2

using let | const

FJS creation x 56,896 ops/sec ±0.32% (94 runs sampled)
CJS creation x 160,658 ops/sec ±0.29% (94 runs sampled)

JSON.stringify array x 3,314 ops/sec ±0.31% (96 runs sampled)
fast-json-stringify array x 8,388 ops/sec ±0.56% (91 runs sampled)

compile-json-stringify array x 7,319 ops/sec ±0.50% (92 runs sampled)
JSON.stringify long string x 10,085 ops/sec ±0.10% (97 runs sampled)

fast-json-stringify long string x 10,087 ops/sec ±0.15% (96 runs sampled)
compile-json-stringify long string x 10,069 ops/sec ±0.14% (98 runs sampled)

JSON.stringify short string x 8,644,967 ops/sec ±0.32% (91 runs sampled)
fast-json-stringify short string x 46,317,880 ops/sec ±0.41% (96 runs sampled)

compile-json-stringify short string x 38,401,762 ops/sec ±0.88% (97 runs sampled)
JSON.stringify obj x 1,824,375 ops/sec ±0.19% (93 runs sampled)

fast-json-stringify obj x 16,346,021 ops/sec ±0.43% (91 runs sampled)
compile-json-stringify obj x 22,268,550 ops/sec ±0.80% (97 runs sampled)

var (master)

FJS creation x 56,203 ops/sec ±0.58% (94 runs sampled)
CJS creation x 161,716 ops/sec ±0.33% (92 runs sampled)

JSON.stringify array x 3,310 ops/sec ±0.24% (95 runs sampled)
fast-json-stringify array x 8,026 ops/sec ±2.21% (87 runs sampled)

compile-json-stringify array x 8,131 ops/sec ±0.35% (94 runs sampled)
JSON.stringify long string x 10,076 ops/sec ±0.16% (97 runs sampled)

fast-json-stringify long string x 10,082 ops/sec ±0.19% (95 runs sampled)
compile-json-stringify long string x 10,067 ops/sec ±0.19% (98 runs sampled)

JSON.stringify short string x 8,695,700 ops/sec ±0.35% (95 runs sampled)
fast-json-stringify short string x 47,173,708 ops/sec ±0.17% (95 runs sampled)

compile-json-stringify short string x 38,136,956 ops/sec ±0.42% (98 runs sampled)
JSON.stringify obj x 1,833,705 ops/sec ±0.14% (96 runs sampled)

fast-json-stringify obj x 16,740,274 ops/sec ±1.56% (92 runs sampled)
compile-json-stringify obj x 22,381,926 ops/sec ±0.76% (96 runs sampled)

[zekth]

lgtm

[zekth]

Miss this one

[mcollina]

lgtm (I do not see regressions in the benchmarks)