mathjs/src/expression/transform/forEach.transform.js

Math.js is an extensive math library for JavaScript and Node.js. It features a flexible expression parser with support for symbolic computation, comes with a large set of built-in functions and constants, and offers an integrated solution to work with dif

import { isFunctionAssignmentNode, isSymbolNode } from '../../utils/is'
import { maxArgumentCount } from '../../utils/function'
import { forEach } from '../../utils/array'
import { factory } from '../../utils/factory'
import { compileInlineExpression } from './utils/compileInlineExpression'

const name = 'forEach'
const dependencies = ['typed']

export const createForEachTransform = /* #__PURE__ */ factory(name, dependencies, ({ typed }) => {
  /**
   * Attach a transform function to math.forEach
   * Adds a property transform containing the transform function.
   *
   * This transform creates a one-based index instead of a zero-based index
   */
  function forEachTransform (args, math, scope) {
    let x, callback

    if (args[0]) {
      x = args[0].compile().evaluate(scope)
    }

    if (args[1]) {
      if (isSymbolNode(args[1]) || isFunctionAssignmentNode(args[1])) {
        // a function pointer, like forEach([3, -2, 5], myTestFunction)
        callback = args[1].compile().evaluate(scope)
      } else {
        // an expression like forEach([3, -2, 5], x > 0 ? callback1(x) : callback2(x) )
        callback = compileInlineExpression(args[1], math, scope)
      }
    }

    return _forEach(x, callback)
  }
  forEachTransform.rawArgs = true

  // one-based version of forEach
  const _forEach = typed('forEach', {
    'Array | Matrix, function': function (array, callback) {
      // figure out what number of arguments the callback function expects
      const args = maxArgumentCount(callback)

      const recurse = function (value, index) {
        if (Array.isArray(value)) {
          forEach(value, function (child, i) {
            // we create a copy of the index array and append the new index value
            recurse(child, index.concat(i + 1)) // one based index, hence i+1
          })
        } else {
          // invoke the callback function with the right number of arguments
          if (args === 1) {
            callback(value)
          } else if (args === 2) {
            callback(value, index)
          } else { // 3 or -1
            callback(value, index, array)
          }
        }
      }
      recurse(array.valueOf(), []) // pass Array
    }
  })

  return forEachTransform
}, { isTransformFunction: true })