mathjs/src/utils/object.js

'use strict'

const isBigNumber = require('./bignumber/isBigNumber')

/**
 * Clone an object
 *
 *     clone(x)
 *
 * Can clone any primitive type, array, and object.
 * If x has a function clone, this function will be invoked to clone the object.
 *
 * @param {*} x
 * @return {*} clone
 */
exports.clone = function clone (x) {
  const type = typeof x

  // immutable primitive types
  if (type === 'number' || type === 'string' || type === 'boolean' ||
      x === null || x === undefined) {
    return x
  }

  // use clone function of the object when available
  if (typeof x.clone === 'function') {
    return x.clone()
  }

  // array
  if (Array.isArray(x)) {
    return x.map(function (value) {
      return clone(value)
    })
  }

  if (x instanceof Date) return new Date(x.valueOf())
  if (isBigNumber(x)) return x // bignumbers are immutable
  if (x instanceof RegExp) throw new TypeError('Cannot clone ' + x) // TODO: clone a RegExp

  // object
  return exports.map(x, clone)
}

/**
 * Apply map to all properties of an object
 * @param {Object} object
 * @param {function} callback
 * @return {Object} Returns a copy of the object with mapped properties
 */
exports.map = function (object, callback) {
  const clone = {}

  for (const key in object) {
    if (exports.hasOwnProperty(object, key)) {
      clone[key] = callback(object[key])
    }
  }

  return clone
}

/**
 * Extend object a with the properties of object b
 * @param {Object} a
 * @param {Object} b
 * @return {Object} a
 */
exports.extend = function (a, b) {
  for (const prop in b) {
    if (exports.hasOwnProperty(b, prop)) {
      a[prop] = b[prop]
    }
  }
  return a
}

/**
 * Deep extend an object a with the properties of object b
 * @param {Object} a
 * @param {Object} b
 * @returns {Object}
 */
exports.deepExtend = function deepExtend (a, b) {
  // TODO: add support for Arrays to deepExtend
  if (Array.isArray(b)) {
    throw new TypeError('Arrays are not supported by deepExtend')
  }

  for (const prop in b) {
    if (exports.hasOwnProperty(b, prop)) {
      if (b[prop] && b[prop].constructor === Object) {
        if (a[prop] === undefined) {
          a[prop] = {}
        }
        if (a[prop].constructor === Object) {
          deepExtend(a[prop], b[prop])
        } else {
          a[prop] = b[prop]
        }
      } else if (Array.isArray(b[prop])) {
        throw new TypeError('Arrays are not supported by deepExtend')
      } else {
        a[prop] = b[prop]
      }
    }
  }
  return a
}

/**
 * Deep test equality of all fields in two pairs of arrays or objects.
 * @param {Array | Object} a
 * @param {Array | Object} b
 * @returns {boolean}
 */
exports.deepEqual = function deepEqual (a, b) {
  let prop, i, len
  if (Array.isArray(a)) {
    if (!Array.isArray(b)) {
      return false
    }

    if (a.length !== b.length) {
      return false
    }

    for (i = 0, len = a.length; i < len; i++) {
      if (!exports.deepEqual(a[i], b[i])) {
        return false
      }
    }
    return true
  } else if (a instanceof Object) {
    if (Array.isArray(b) || !(b instanceof Object)) {
      return false
    }

    for (prop in a) {
      // noinspection JSUnfilteredForInLoop
      if (!exports.deepEqual(a[prop], b[prop])) {
        return false
      }
    }
    for (prop in b) {
      // noinspection JSUnfilteredForInLoop
      if (!exports.deepEqual(a[prop], b[prop])) {
        return false
      }
    }
    return true
  } else {
    return (a === b)
  }
}

/**
 * Test whether the current JavaScript engine supports Object.defineProperty
 * @returns {boolean} returns true if supported
 */
exports.canDefineProperty = function () {
  // test needed for broken IE8 implementation
  try {
    if (Object.defineProperty) {
      Object.defineProperty({}, 'x', { get: function () {} })
      return true
    }
  } catch (e) {}

  return false
}

/**
 * Attach a lazy loading property to a constant.
 * The given function `fn` is called once when the property is first requested.
 * On older browsers (<IE8), the function will fall back to direct evaluation
 * of the properties value.
 * @param {Object} object   Object where to add the property
 * @param {string} prop     Property name
 * @param {Function} fn     Function returning the property value. Called
 *                          without arguments.
 */
exports.lazy = function (object, prop, fn) {
  if (exports.canDefineProperty()) {
    let _uninitialized = true
    let _value
    Object.defineProperty(object, prop, {
      get: function () {
        if (_uninitialized) {
          _value = fn()
          _uninitialized = false
        }
        return _value
      },

      set: function (value) {
        _value = value
        _uninitialized = false
      },

      configurable: true,
      enumerable: true
    })
  } else {
    // fall back to immediate evaluation
    object[prop] = fn()
  }
}

/**
 * Traverse a path into an object.
 * When a namespace is missing, it will be created
 * @param {Object} object
 * @param {string} path   A dot separated string like 'name.space'
 * @return {Object} Returns the object at the end of the path
 */
exports.traverse = function (object, path) {
  let obj = object

  if (path) {
    const names = path.split('.')
    for (let i = 0; i < names.length; i++) {
      const name = names[i]
      if (!(name in obj)) {
        obj[name] = {}
      }
      obj = obj[name]
    }
  }

  return obj
}

/**
 * A safe hasOwnProperty
 * @param {Object} object
 * @param {string} property
 */
exports.hasOwnProperty = function (object, property) {
  return object && Object.hasOwnProperty.call(object, property)
}

/**
 * Test whether an object is a factory. a factory has fields:
 *
 * - factory: function (type: Object, config: Object, load: function, typed: function [, math: Object])   (required)
 * - name: string (optional)
 * - path: string    A dot separated path (optional)
 * - math: boolean   If true (false by default), the math namespace is passed
 *                   as fifth argument of the factory function
 *
 * @param {*} object
 * @returns {boolean}
 */
exports.isFactory = function (object) {
  return object && typeof object.factory === 'function'
}