Add support for getting the index in the iterators (../index)

Author: TotalTechGeek

.gitignore

@@ -1,3 +1,4 @@
+experiments/
 node_modules/
 .nyc_output
 coverage

.npmignore

@@ -8,4 +8,5 @@ bench/
 .github/
 .eslintrc.json
 perf*.js
-*.test.js
+*.test.js
+experiments/

async_iterators.js

@@ -4,30 +4,34 @@
 // I am supporting filter, reduce, some, every, map
 export async function filter (arr, iter) {
   const result = []
+  let index = 0
   for (const item of arr) {
-    if (await iter(item)) result.push(item)
+    if (await iter(item, index++)) result.push(item)
   }
   return result
 }
 
 export async function some (arr, iter) {
+  let index = 0
   for (const item of arr) {
-    if (await iter(item)) return true
+    if (await iter(item, index++)) return true
   }
   return false
 }
 
 export async function every (arr, iter) {
+  let index = 0
   for (const item of arr) {
-    if (!(await iter(item))) return false
+    if (!(await iter(item, index++))) return false
   }
   return true
 }
 
 export async function map (arr, iter) {
   const result = []
+  let index = 0
   for (const item of arr) {
-    result.push(await iter(item))
+    result.push(await iter(item, index++))
   }
   return result
 }

compiler.js

@@ -28,6 +28,7 @@ import asyncIterators from './async_iterators.js'
  * @property {*} [yieldUsed]
  * @property {Boolean} [useContext]
  * @property {Boolean} [avoidInlineAsync]
+ * @property {string} [extraArguments]
  *
  */
 
@@ -497,7 +498,7 @@ function processBuiltString (method, str, buildState) {
     }
   }
 
-  const final = `(state, values, methods, gen, notTraversed, Override, asyncIterators, r, rAsync) => ${buildState.asyncDetected ? 'async' : ''} (context ${
+  const final = `(state, values, methods, gen, notTraversed, Override, asyncIterators, r, rAsync) => ${buildState.asyncDetected ? 'async' : ''} (context ${buildState.extraArguments ? ',' + buildState.extraArguments : ''} ${
     buildState.yieldUsed ? ', resumable = {}' : ''
   }) => { ${copyStateCall} const result = ${str}; return result }`
 

defaultMethods.js

@@ -443,9 +443,9 @@ function createArrayIterativeMethod (name) {
         engine.run(selector, context, {
           above
         }) || []
-      return selector[name]((i) => {
+      return selector[name]((i, index) => {
         return engine.run(mapper, i, {
-          above: [selector, context, ...above]
+          above: [{ item: selector, index }, context, ...above]
         })
       })
     },
@@ -456,9 +456,9 @@ function createArrayIterativeMethod (name) {
         (await engine.run(selector, context, {
           above
         })) || []
-      return asyncIterators[name](selector, (i) => {
+      return asyncIterators[name](selector, (i, index) => {
         return engine.run(mapper, i, {
-          above: [selector, context, ...above]
+          above: [{ item: selector, index }, context, ...above]
         })
       })
     },
@@ -470,8 +470,9 @@ function createArrayIterativeMethod (name) {
       const mapState = {
         ...buildState,
         state: {},
-        above: [selector, state, ...above],
-        avoidInlineAsync: true
+        above: [{ item: selector }, state, ...above],
+        avoidInlineAsync: true,
+        iteratorCompile: true
       }
       mapper = build(mapper, mapState)
       buildState.useContext = buildState.useContext || mapState.useContext
@@ -841,6 +842,11 @@ defaultMethods.var.compile = function (data, buildState) {
     typeof data === 'number' ||
     (Array.isArray(data) && data.length <= 2)
   ) {
+    if (data === '../index' && buildState.iteratorCompile) {
+      buildState.extraArguments = 'index'
+      return 'index'
+    }
+
     if (Array.isArray(data)) {
       key = data[0]
       defaultValue = typeof data[1] === 'undefined' ? null : data[1]

general.test.js

@@ -154,6 +154,15 @@ describe('Various Test Cases', () => {
     for (const engine of [...normalEngines, ...permissiveEngines]) await testEngine(engine, { var: '\\\\foo' }, { '\\foo': 2 }, 2)
   })
 
+  it('is able to access the index in the iterators', async () => {
+    for (const engine of [...normalEngines, ...permissiveEngines]) await testEngine(engine, { map: [[0, 1, 2, 3], { '+': [{ var: '' }, { var: '../index' }] }] }, {}, [0, 2, 4, 6])
+  })
+
+  // This is not fully supported right now.
+  // it('is able to access the source array in the iterators', async () => {
+  //   for (const engine of [...normalEngines, ...permissiveEngines]) await testEngine(engine, { map: [[0, 1, 2, 3], { '+': [{ var: '' }, { var: '../item.2' }] }] }, {}, [2, 3, 4, 5])
+  // })
+
   it('should be able to handle various instances of "in" with good, bad and invalid data', async () => {
     const rule = {
       in: ['Spring', { var: 'city' }]