lodash源码学习curry,curryRight

//curry.js

var createWrap = require('./_createWrap');//函数包装方法

var WRAP_CURRY_FLAG = 8;

/**
 * 
 *
 * _.curry.placeholder的值默认为`_`
 *
 * @param {Function} func 需要柯里化的函数.
 * @param {number} [arity=func.length] 参数数量.
 * @param- {Object} [guard] 是否能作为遍历参数被像_.map这样的方法调用.
 * @returns {Function} 返回柯里化之后的函数.
 * @example
 *
 * var abc = function(a, b, c) {
 *   return [a, b, c];
 * };
 *
 * var curried = _.curry(abc);
 *
 * curried(1)(2)(3);
 * // => [1, 2, 3]
 *
 * curried(1, 2)(3);
 * // => [1, 2, 3]
 *
 * curried(1, 2, 3);
 * // => [1, 2, 3]
 *
 * // Curried with placeholders.
 * curried(1)(_, 3)(2);
 * // => [1, 2, 3]
 */
function curry(func, arity, guard) {
  arity = guard ? undefined : arity;
  //调用createWrap方法，传入位掩码标识为curry
  var result = createWrap(func, WRAP_CURRY_FLAG, undefined, undefined, undefined, undefined, undefined, arity);
  result.placeholder = curry.placeholder;
  return result;//返回包装后的方法
}

// 默认占位符赋值.
curry.placeholder = {};

module.exports = curry;

//_createWrap.js

var baseSetData = require('./_baseSetData'),
    createBind = require('./_createBind'),
    createCurry = require('./_createCurry'),
    createHybrid = require('./_createHybrid'),
    createPartial = require('./_createPartial'),
    getData = require('./_getData'),
    mergeData = require('./_mergeData'),
    setData = require('./_setData'),
    setWrapToString = require('./_setWrapToString'),
    toInteger = require('./toInteger');

var FUNC_ERROR_TEXT = 'Expected a function';

//各种方法的位掩码标识
var WRAP_BIND_FLAG = 1,
    WRAP_BIND_KEY_FLAG = 2,
    WRAP_CURRY_FLAG = 8,
    WRAP_CURRY_RIGHT_FLAG = 16,
    WRAP_PARTIAL_FLAG = 32,
    WRAP_PARTIAL_RIGHT_FLAG = 64;

var nativeMax = Math.max;//原生最大值方法

/**
 * 创建一个函数，该函数可以创建或调用func用可选的this和部分应用的参数.
 *
 * @param {Function|string} func 需要包装的函数.
 * @param {number} bitmask 位掩码标识
 * @param {*} [thisArg] func的this对象
 * @param {Array} [partials] 应用的参数
 * @param {Array} [holders] 占位符的索引
 * @param {Array} [argPos] .
 * @param {number} [ary] .
 * @param {number} [arity] 可用参数数量.
 * @returns {Function} 返回包装之后的函数.
 */
 //lodash使用BitMask来进行各种方法的表示，BitMask使用方法可以看 http://geek.****.net/news/detail/73343

function createWrap(func, bitmask, thisArg, partials, holders, argPos, ary, arity) {
  var isBindKey = bitmask & WRAP_BIND_KEY_FLAG;//是否是bindKey方法（不是）
  if (!isBindKey && typeof func != 'function') {
    throw new TypeError(FUNC_ERROR_TEXT);
  }
  var length = partials ? partials.length : 0;//应用的参数个数，为0
  if (!length) {
    bitmask &= ~(WRAP_PARTIAL_FLAG | WRAP_PARTIAL_RIGHT_FLAG);//清除WRAP_PARTIAL_FLAG和WRAP_PARTIAL_RIGHT_FLAG
    partials = holders = undefined;//部分参数和占位符索引都为undefined
  }
  ary = ary === undefined ? ary : nativeMax(toInteger(ary), 0);
  arity = arity === undefined ? arity : toInteger(arity);//将arity转为整形
  length -= holders ? holders.length : 0;//跳过

  if (bitmask & WRAP_PARTIAL_RIGHT_FLAG) {//是否是WRAP_PARTIAL_RIGHT_FLAG(不是，跳过)
    var partialsRight = partials,
        holdersRight = holders;

    partials = holders = undefined;
  }
  var data = isBindKey ? undefined : getData(func);//得到func的元数据

  var newData = [
    func, bitmask, thisArg, partials, holders, partialsRight, holdersRight,
    argPos, ary, arity
  ];//将所有参数赋值给newData

  if (data) {
    mergeData(newData, data);
  }
  func = newData[0];
  bitmask = newData[1];
  thisArg = newData[2];
  partials = newData[3];
  holders = newData[4];
  arity = newData[9] = newData[9] === undefined
    ? (isBindKey ? 0 : func.length)
    : nativeMax(newData[9] - length, 0);//处理一下arity，默认为func的长度

  if (!arity && bitmask & (WRAP_CURRY_FLAG | WRAP_CURRY_RIGHT_FLAG)) {//如果没有arity,清除curry和curryRight标识
    bitmask &= ~(WRAP_CURRY_FLAG | WRAP_CURRY_RIGHT_FLAG);
  }
  if (!bitmask || bitmask == WRAP_BIND_FLAG) {
    var result = createBind(func, bitmask, thisArg);
  } else if (bitmask == WRAP_CURRY_FLAG || bitmask == WRAP_CURRY_RIGHT_FLAG) {//如果传了arity,进入这里，调用createCurry方法
    result = createCurry(func, bitmask, arity);
  } else if ((bitmask == WRAP_PARTIAL_FLAG || bitmask == (WRAP_BIND_FLAG | WRAP_PARTIAL_FLAG)) && !holders.length) {
    result = createPartial(func, bitmask, thisArg, partials);
  } else {
    result = createHybrid.apply(undefined, newData);
  }
  var setter = data ? baseSetData : setData;//设置data的元数据（暂不分析）
  return setWrapToString(setter(result, newData), func, bitmask);//给包装之后的方法添加元数据（用于优化），添加toStirng方法，并返回func(具体实现暂不分析)
}

module.exports = createWrap;

//_createCurry.js

var apply = require('./_apply'),//同Function.apply
    createCtor = require('./_createCtor'),//创建一个可以创建函数实例的方法
    createHybrid = require('./_createHybrid'),//混合包装方法
    createRecurry = require('./_createRecurry'),//createRecurry方法
    getHolder = require('./_getHolder'),//得到占位符
    replaceHolders = require('./_replaceHolders'),//替换占位符
    root = require('./_root');//根元素，浏览器为window,node为global

/**
 * 创建一个包装func，使其实现柯里化的方法.
 *
 * @private
 * @param {Function} func The function to wrap.
 * @param {number} bitmask The bitmask flags. See `createWrap` for more details.
 * @param {number} arity The arity of `func`.
 * @returns {Function} Returns the new wrapped function.
 */
function createCurry(func, bitmask, arity) {
  var Ctor = createCtor(func);//创建实例生成器

  function wrapper() {
    var length = arguments.length,//参数个数
        args = Array(length),//参数数组
        index = length,//参数索引
        placeholder = getHolder(wrapper);//得到占位符

    while (index--) {//遍历参数，将参数转化为args数组
      args[index] = arguments[index];
    }
    var holders = (length < 3 && args[0] !== placeholder && args[length - 1] !== placeholder)
      ? []
      : replaceHolders(args, placeholder);//得到占位符索引

    length -= holders.length;//参数个数减去占位符的个数
    if (length < arity) {//如果参数个数少于arity,调用createRecurry，并返回得到的新的函数
      return createRecurry(
        func, bitmask, createHybrid, wrapper.placeholder, undefined,
        args, holders, undefined, undefined, arity - length);
    }
    var fn = (this && this !== root && this instanceof wrapper) ? Ctor : func;
    return apply(fn, this, args);//调用fn
  }
  return wrapper;
}

module.exports = createCurry;

//_createRecurry.js

var isLaziable = require('./_isLaziable'),//是否是一个惰性函数（在缓存中是否存在）
    setData = require('./_setData'),//设置元数据
    setWrapToString = require('./_setWrapToString');//添加toString方法

//各种位掩码
var WRAP_BIND_FLAG = 1,
    WRAP_BIND_KEY_FLAG = 2,
    WRAP_CURRY_BOUND_FLAG = 4,
    WRAP_CURRY_FLAG = 8,
    WRAP_PARTIAL_FLAG = 32,
    WRAP_PARTIAL_RIGHT_FLAG = 64;

/**
 * 创建一个包装func使其持续柯里化的方法.
 *
 * @private
 * @param {Function} func 需要包装的方法.
 * @param {number} bitmask 位掩码标识.
 * @param {Function} wrapFunc 包装函数.
 * @param {*} placeholder 占位符的值.
 * @param {*} [thisArg] .
 * @param {Array} [partials] 提前传入的参数.
 * @param {Array} [holders] 占位符索引.
 * @param {Array} [argPos] The argument positions of the new function.
 * @param {number} [ary] The arity cap of `func`.
 * @param {number} [arity] 参数个数.
 * @returns {Function} 返回新的包装方法.
 */
function createRecurry(func, bitmask, wrapFunc, placeholder, thisArg, partials, holders, argPos, ary, arity) {
  var isCurry = bitmask & WRAP_CURRY_FLAG,//是curry
      newHolders = isCurry ? holders : undefined,
      newHoldersRight = isCurry ? undefined : holders,
      newPartials = isCurry ? partials : undefined,
      newPartialsRight = isCurry ? undefined : partials;

  bitmask |= (isCurry ? WRAP_PARTIAL_FLAG : WRAP_PARTIAL_RIGHT_FLAG);//添加partial标识
  bitmask &= ~(isCurry ? WRAP_PARTIAL_RIGHT_FLAG : WRAP_PARTIAL_FLAG);//清除partialRight标识

  if (!(bitmask & WRAP_CURRY_BOUND_FLAG)) {
    bitmask &= ~(WRAP_BIND_FLAG | WRAP_BIND_KEY_FLAG);
  }
  var newData = [
    func, bitmask, thisArg, newPartials, newHolders, newPartialsRight,
    newHoldersRight, argPos, ary, arity
  ];

  var result = wrapFunc.apply(undefined, newData);//调用wrapFunc方法
  if (isLaziable(func)) {//如果在缓存中存在，设置元数据
    setData(result, newData);
  }
  result.placeholder = placeholder;
  return setWrapToString(result, func, bitmask);//添加toString方法并返回包装函数
}

module.exports = createRecurry;

//_createHybrid.js

var composeArgs = require('./_composeArgs'),//组合参数方法，见源码学习（7）
    composeArgsRight = require('./_composeArgsRight'),
    countHolders = require('./_countHolders'),
    createCtor = require('./_createCtor'),
    createRecurry = require('./_createRecurry'),
    getHolder = require('./_getHolder'),
    reorder = require('./_reorder'),
    replaceHolders = require('./_replaceHolders'),
    root = require('./_root');

//位掩码标识
var WRAP_BIND_FLAG = 1,
    WRAP_BIND_KEY_FLAG = 2,
    WRAP_CURRY_FLAG = 8,
    WRAP_CURRY_RIGHT_FLAG = 16,
    WRAP_ARY_FLAG = 128,
    WRAP_FLIP_FLAG = 512;

/**
 * 创建一个包装函数，调用func使用可选的thisArg，应用部分参数和柯里化.
 *
 * @param {Function|string} func 需要包装的方法.
 * @param {number} bitmask 位掩码标识
 * @param {*} [thisArg] .
 * @param {Array} [partials] 实现传入的参数.
 * @param {Array} [holders] 占位符.
 * @param {Array} [partialsRight] .
 * @param {Array} [holdersRight] .
 * @param {Array} [argPos] .
 * @param {number} [ary] .
 * @param {number} [arity] 可用函数参数数量.
 * @returns {Function} 返回新的包装函数.
 */
function createHybrid(func, bitmask, thisArg, partials, holders, partialsRight, holdersRight, argPos, ary, arity) {
  var isAry = bitmask & WRAP_ARY_FLAG,
      isBind = bitmask & WRAP_BIND_FLAG,
      isBindKey = bitmask & WRAP_BIND_KEY_FLAG,
      isCurried = bitmask & (WRAP_CURRY_FLAG | WRAP_CURRY_RIGHT_FLAG),//是curry方法
      isFlip = bitmask & WRAP_FLIP_FLAG,
      Ctor = isBindKey ? undefined : createCtor(func);

  function wrapper() {
    var length = arguments.length,//参数个数
        args = Array(length),//保存所有参数
        index = length;//参数数组索引

    while (index--) {//遍历参数，将所有参数存入args
      args[index] = arguments[index];
    }
    if (isCurried) {
      var placeholder = getHolder(wrapper),//得到占位符标识
          holdersCount = countHolders(args, placeholder);//占位符数量
    }
    if (partials) {//执行composeArgs，对参数进行组合
      args = composeArgs(args, partials, holders, isCurried);
    }
    if (partialsRight) {
      args = composeArgsRight(args, partialsRight, holdersRight, isCurried);
    }
    length -= holdersCount;//参数个数减去占位符数量
    if (isCurried && length < arity) {//如果个数比arity小
      var newHolders = replaceHolders(args, placeholder);//得到新的占位符索引位置
      return createRecurry(
        func, bitmask, createHybrid, wrapper.placeholder, thisArg,
        args, newHolders, argPos, ary, arity - length
      );//再次调用createRecurry方法，继续柯里化（会一直循环调用createRecurry和createHybrid方法，直到参数传完整）
    }
    var thisBinding = isBind ? thisArg : this,
        fn = isBindKey ? thisBinding[func] : func;

    length = args.length;//参数长度
    if (argPos) {
      args = reorder(args, argPos);
    } else if (isFlip && length > 1) {
      args.reverse();
    }
    if (isAry && ary < length) {
      args.length = ary;
    }
    if (this && this !== root && this instanceof wrapper) {
      fn = Ctor || createCtor(fn);
    }
    return fn.apply(thisBinding, args);//调用fn，并且传入args
  }
  return wrapper;//返回包装方法
}
module.exports = createHybrid;

//curryRight.js

var createWrap = require('./_createWrap');//包装方法

var WRAP_CURRY_RIGHT_FLAG = 16;//curryRight位掩码标识

/**
 *
 *
 * _.curryRight.placeholder默认值为`_`
 *
 * @param {Function} func 需要柯里化的函数.
 * @param {number} [arity=func.length] 参数数量.
 * @param- {Object} [guard] 是否能作为遍历参数被像_.map这样的方法调用.
 * @returns {Function} 返回柯里化之后的函数.
 * @example
 *
 * var abc = function(a, b, c) {
 *   return [a, b, c];
 * };
 *
 * var curried = _.curryRight(abc);
 *
 * curried(3)(2)(1);
 * // => [1, 2, 3]
 *
 * curried(2, 3)(1);
 * // => [1, 2, 3]
 *
 * curried(1, 2, 3);
 * // => [1, 2, 3]
 *
 * // Curried with placeholders.
 * curried(3)(1, _)(2);
 * // => [1, 2, 3]
 */
function curryRight(func, arity, guard) {//除了传入位掩码的不同和curry一模一样
  arity = guard ? undefined : arity;
  var result = createWrap(func, WRAP_CURRY_RIGHT_FLAG, undefined, undefined, undefined, undefined, undefined, arity);
  result.placeholder = curryRight.placeholder;
  return result;
}

// Assign default placeholders.
curryRight.placeholder = {};

module.exports = curryRight;

//_createRecurry.js

var isLaziable = require('./_isLaziable'),//是否是一个惰性函数（在缓存中是否存在）
    setData = require('./_setData'),//设置元数据
    setWrapToString = require('./_setWrapToString');//添加toString方法

//各种位掩码
var WRAP_BIND_FLAG = 1,
    WRAP_BIND_KEY_FLAG = 2,
    WRAP_CURRY_BOUND_FLAG = 4,
    WRAP_CURRY_FLAG = 8,
    WRAP_PARTIAL_FLAG = 32,
    WRAP_PARTIAL_RIGHT_FLAG = 64;

/**
 * 创建一个包装func使其持续柯里化的方法.
 *
 * @private
 * @param {Function} func 需要包装的方法.
 * @param {number} bitmask 位掩码标识.
 * @param {Function} wrapFunc 包装函数.
 * @param {*} placeholder 占位符的值.
 * @param {*} [thisArg] .
 * @param {Array} [partials] 提前传入的参数.
 * @param {Array} [holders] 占位符索引.
 * @param {Array} [argPos] The argument positions of the new function.
 * @param {number} [ary] The arity cap of `func`.
 * @param {number} [arity] 参数个数.
 * @returns {Function} 返回新的包装方法.
 */
function createRecurry(func, bitmask, wrapFunc, placeholder, thisArg, partials, holders, argPos, ary, arity) {
  var isCurry = bitmask & WRAP_CURRY_FLAG,//不是curry
      newHolders = isCurry ? holders : undefined,
      newHoldersRight = isCurry ? undefined : holders,//设置newHoldersRight
      newPartials = isCurry ? partials : undefined,
      newPartialsRight = isCurry ? undefined : partials;//设置newPartialsRight

  bitmask |= (isCurry ? WRAP_PARTIAL_FLAG : WRAP_PARTIAL_RIGHT_FLAG);//添加partialRight标识
  bitmask &= ~(isCurry ? WRAP_PARTIAL_RIGHT_FLAG : WRAP_PARTIAL_FLAG);//清除partial标识

  if (!(bitmask & WRAP_CURRY_BOUND_FLAG)) {
    bitmask &= ~(WRAP_BIND_FLAG | WRAP_BIND_KEY_FLAG);
  }
  var newData = [
    func, bitmask, thisArg, newPartials, newHolders, newPartialsRight,
    newHoldersRight, argPos, ary, arity
  ];

  var result = wrapFunc.apply(undefined, newData);//调用wrapFunc方法
  if (isLaziable(func)) {//如果在缓存中存在，设置元数据
    setData(result, newData);
  }
  result.placeholder = placeholder;
  return setWrapToString(result, func, bitmask);//添加toString方法并返回包装函数
}

module.exports = createRecurry;

//_createHybrid.js

var composeArgs = require('./_composeArgs'),//组合参数方法
    composeArgsRight = require('./_composeArgsRight'),//从右向左组合参数
    countHolders = require('./_countHolders'),
    createCtor = require('./_createCtor'),
    createRecurry = require('./_createRecurry'),
    getHolder = require('./_getHolder'),
    reorder = require('./_reorder'),
    replaceHolders = require('./_replaceHolders'),
    root = require('./_root');

//位掩码标识
var WRAP_BIND_FLAG = 1,
    WRAP_BIND_KEY_FLAG = 2,
    WRAP_CURRY_FLAG = 8,
    WRAP_CURRY_RIGHT_FLAG = 16,
    WRAP_ARY_FLAG = 128,
    WRAP_FLIP_FLAG = 512;

/**
 * 创建一个包装函数，调用func使用可选的thisArg，应用部分参数和柯里化.
 *
 * @param {Function|string} func 需要包装的方法.
 * @param {number} bitmask 位掩码标识
 * @param {*} [thisArg] .
 * @param {Array} [partials] 实现传入的参数.
 * @param {Array} [holders] 占位符.
 * @param {Array} [partialsRight] .
 * @param {Array} [holdersRight] .
 * @param {Array} [argPos] .
 * @param {number} [ary] .
 * @param {number} [arity] 可用函数参数数量.
 * @returns {Function} 返回新的包装函数.
 */
function createHybrid(func, bitmask, thisArg, partials, holders, partialsRight, holdersRight, argPos, ary, arity) {
  var isAry = bitmask & WRAP_ARY_FLAG,
      isBind = bitmask & WRAP_BIND_FLAG,
      isBindKey = bitmask & WRAP_BIND_KEY_FLAG,
      isCurried = bitmask & (WRAP_CURRY_FLAG | WRAP_CURRY_RIGHT_FLAG),//是curry方法
      isFlip = bitmask & WRAP_FLIP_FLAG,
      Ctor = isBindKey ? undefined : createCtor(func);

  function wrapper() {
    var length = arguments.length,//参数个数
        args = Array(length),//保存所有参数
        index = length;//参数数组索引

    while (index--) {//遍历参数，将所有参数存入args
      args[index] = arguments[index];
    }
    if (isCurried) {
      var placeholder = getHolder(wrapper),//得到占位符标识
          holdersCount = countHolders(args, placeholder);//占位符数量
    }
    if (partials) {
      args = composeArgs(args, partials, holders, isCurried);
    }
    if (partialsRight) {//执行composeArgsRight方法，组合参数
      args = composeArgsRight(args, partialsRight, holdersRight, isCurried);
    }
    length -= holdersCount;//参数个数减去占位符数量
    if (isCurried && length < arity) {//如果个数比arity小
      var newHolders = replaceHolders(args, placeholder);//得到新的占位符索引位置
      return createRecurry(
        func, bitmask, createHybrid, wrapper.placeholder, thisArg,
        args, newHolders, argPos, ary, arity - length
      );//再次调用createRecurry方法，继续柯里化（会一直循环调用createRecurry和createHybrid方法，直到参数传完整）
    }
    var thisBinding = isBind ? thisArg : this,
        fn = isBindKey ? thisBinding[func] : func;

    length = args.length;//参数长度
    if (argPos) {
      args = reorder(args, argPos);
    } else if (isFlip && length > 1) {
      args.reverse();
    }
    if (isAry && ary < length) {
      args.length = ary;
    }
    if (this && this !== root && this instanceof wrapper) {
      fn = Ctor || createCtor(fn);
    }
    return fn.apply(thisBinding, args);//调用fn，并且传入args
  }
  return wrapper;//返回包装方法
}
module.exports = createHybrid;

//_composeArgsRight.js

var nativeMax = Math.max;//原生求最大值方法

/**
 * 和composeArgs很像，只是组合参数的方向相反
 *
* @private
 * @param {Array} args 提供的参数.
 * @param {Array} partials 提前传入的参数.
 * @param {Array} holders 提前传入参数中的占位符索引.
 * @params {boolean} [isCurried] 指定是否组成一个柯里化函数.
 * @returns {Array} 返回新的参数集合.
 */
function composeArgsRight(args, partials, holders, isCurried) {
  var argsIndex = -1,//参数索引
      argsLength = args.length,//传入参数个数
      holdersIndex = -1,//占位符索引
      holdersLength = holders.length,//占位符个数
      rightIndex = -1,//提前传入参数索引
      rightLength = partials.length,//提前传入参数个数
      rangeLength = nativeMax(argsLength - holdersLength, 0),//实际传入参数个数
      result = Array(rangeLength + rightLength),//结果参数数组
      isUncurried = !isCurried;

  while (++argsIndex < rangeLength) {//遍历传入参数，将其传入result
    result[argsIndex] = args[argsIndex];
  }
  var offset = argsIndex;
  while (++rightIndex < rightLength) {//遍历partials，将其传入result
    result[offset + rightIndex] = partials[rightIndex];
  }
  while (++holdersIndex < holdersLength) {//遍历占位符索引，将result中对应索引的值，换成传入的参数对应的值
    if (isUncurried || argsIndex < argsLength) {
      result[offset + holders[holdersIndex]] = args[argsIndex++];
    }
  }
  return result;//返回生成的完整参数数组
}

module.exports = composeArgsRight;