Improve map

npm/index.js

@@ -68,7 +68,7 @@ function transform(json, code) {
     let s = code.substring(4, code.length - 1)
     if (s[0] === '.') s = 'x' + s
     return eval(`(function () {
-      return this.map(x => apply(x, ${s}))
+      return this.map((x, i) => apply(${s}, x, i))
     })`).call(json)
   }
 
@@ -76,11 +76,11 @@ function transform(json, code) {
     return ${code}
   })`).call(json)
 
-  return apply(json, fn)
+  return apply(fn, json)
 }
 
-function apply(json, fn) {
-  if (typeof fn === 'function') return fn(json)
+function apply(fn, ...args) {
+  if (typeof fn === 'function') return fn(...args)
   return fn
 }
 

npm/test.js

@@ -63,6 +63,11 @@ void async function main() {
     t.deepEqual(JSON.parse(stdout), ['bar'])
   })
 
+  await test('map passes index', async t => {
+    const {stdout} = await run([1, 2, 3], `'map((x, i) => x * i)'`)
+    t.deepEqual(JSON.parse(stdout), [0, 2, 6])
+  })
+
   await test('flat map works', async t => {
     const {stdout} = await run({master: {foo: [{bar: [{val: 1}]}]}}, '.master.foo[].bar[].val')
     t.deepEqual(JSON.parse(stdout), [1])