@dylanarmstrong/babel-plugin-transform-chain-comparisons v0.0.1

babel-plugin-transform-chain-operators

Add chained comparison operators like Python

Setup

In your babel.config.json, place the following:

  "plugins": [
    "@dylanarmstrong/babel-plugin-transform-chain-comparisons"
  ]

Examples:

// Original
if (a < b < c) {}
// Transform
if (a < b && b < c) {}

// Original
if (a != b != c) {}
// Transform
if (a != b && b != c) {}

// Original
if (a < f() < g()) {}
// Transform
const ref1 = f();
if (a < ref1 && ref1 < g()) {}

// Original
if (f() < g() < h()) {}
// Transform
const ref1 = g();
if (f() < ref1 && ref1 < h()) {}

Caveats:

1. a != b != c does not imply a != c
2. await operators are finicky, a < await f() < b will call await f() twice at the moment. This is intended to be fixed.
3. Functions cannot change a value that is relied on in a subsequent statement f(10) < g() < c with c = 2, b = 1; g = () => b;, and f = (n) => { b = n; return 0; }. This is because the expression g() is cached before any BinaryExpression is called. This is done intentionally to avoid double calling the g() method.