Lodash 源码分析（三）Array

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function head(array) {
   return (array && array.length) ? array[0] : undefined;
}

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module.exports = nth(0);

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module.exports = _curry2(function nth(offset, list) {
  var idx = offset < 0 ? list.length + offset : offset;
  return _isString(list) ? list.charAt(idx) : list[idx];
});

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function nth(array, n) {
   return (array && array.length) ? baseNth(array, toInteger(n)) : undefined;
}

function baseNth(array, n) {
  var length = array.length;
  if (!length) {
    return;
  }
  n += n < 0 ? length : 0;
  return isIndex(n, length) ? array[n] : undefined;
}

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var arrayProto = Array.prototype;
var nativeJoin = arrayProto.join;

function join(array, separator) {
  return array == null ? '' : nativeJoin.call(array, separator);
}

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function join(array,separator) {
    return array == null ? '' : Array.prototype.join.call(array, separator);
}

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<br />var invoker = require('./invoker');
module.exports = invoker(1, 'join');

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module.exports = _curry2(function invoker(arity, method) {
  return curryN(arity + 1, function() {
    var target = arguments[arity];
    if (target != null && _isFunction(target[method])) {
      return target[method].apply(target, Array.prototype.slice.call(arguments, 0, arity));
    }
    throw new TypeError(toString(target) + ' does not have a method named "' + method + '"');
  });
});

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function _join(array,separator){
        return Array.prototype.join.call(array,seprator);
}
var join = _.curry(_join);

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join(_,",")([1,2,3]);
// 1,2,3

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    /**
     * Removes all elements from `array` that `predicate` returns truthy for
     * and returns an array of the removed elements. The predicate is invoked
     * with three arguments: (value, index, array).
     *
     * **Note:** Unlike `_.filter`, this method mutates `array`. Use `_.pull`
     * to pull elements from an array by value.
     *
     * @static
     * @memberOf _
     * @since 2.0.0
     * @category Array
     * @param {Array} array The array to modify.
     * @param {Function} [predicate=_.identity] The function invoked per iteration.
     * @returns {Array} Returns the new array of removed elements.
     * @example
     *
     * var array = [1, 2, 3, 4];
     * var evens = _.remove(array, function(n) {
     *   return n % 2 == 0;
     * });
     *
     * console.log(array);
     * // => [1, 3]
     *
     * console.log(evens);
     * // => [2, 4]
     */
    function remove(array, predicate) {
      var result = [];
      if (!(array && array.length)) {
        return result;
      }
      var index = -1,
          indexes = [],
          length = array.length;

      predicate = getIteratee(predicate, 3);
      while (++index < length) {
        var value = array[index];
        if (predicate(value, index, array)) {
          result.push(value);
          indexes.push(index);
        }
      }
      basePullAt(array, indexes);
      return result;
    }

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    /**
     * The base implementation of `_.pullAt` without support for individual
     * indexes or capturing the removed elements.
     *
     * @private
     * @param {Array} array The array to modify.
     * @param {number[]} indexes The indexes of elements to remove.
     * @returns {Array} Returns `array`.
     */
    function basePullAt(array, indexes) {
      var length = array ? indexes.length : 0,
          lastIndex = length - 1;

      while (length--) {
        var index = indexes[length];
        if (length == lastIndex || index !== previous) {
          var previous = index;
          if (isIndex(index)) {
            splice.call(array, index, 1);
          } else {
            baseUnset(array, index);
          }
        }
      }
      return array;
    }

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/**
 * The base implementation of `unset`.
 *
 * @private
 * @param {Object} object The object to modify.
 * @param {Array|string} path The property path to unset.
 * @returns {boolean} Returns `true` if the property is deleted, else `false`.
 */
function baseUnset(object, path) {
  path = castPath(path, object)
  object = parent(object, path)
  return object == null || delete object[toKey(last(path))]
}

export default baseUnset

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function remove(list,predicated){
  var indexes = [];
    for(var i=0;i < list.length;i++){
      if(predicated(list[i])){
        indexes.push(i);
      }
    }
    for(var idx = indexes.length -1; idx >=0;idx--){
      Array.prototype.splice.call(list,indexes[idx],1);
    }
    return list;
}

var a = [1,2,3,4];
remove(a,function(a){if (a == 3) return true; else return false;});
console.log(a); // [1,2,4]

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/**
 * Removes the sub-list of `list` starting at index `start` and containing
 * `count` elements. _Note that this is not destructive_: it returns a copy of
 * the list with the changes.
 * <small>No lists have been harmed in the application of this function.</small>
 *
 * @func
 * @memberOf R
 * @since v0.2.2
 * @category List
 * @sig Number -> Number -> [a] -> [a]
 * @param {Number} start The position to start removing elements
 * @param {Number} count The number of elements to remove
 * @param {Array} list The list to remove from
 * @return {Array} A new Array with `count` elements from `start` removed.
 * @example
 *
 *      R.remove(2, 3, [1,2,3,4,5,6,7,8]); //=> [1,2,6,7,8]
 */
module.exports = _curry3(function remove(start, count, list) {
  var result = Array.prototype.slice.call(list, 0);
  result.splice(start, count);
  return result;
});

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function remove2(list,predicated){
  return _remove(list,list.length-1,predicated);
}

function _remove(list,idx,predicated){
  if(predicated(list[idx])){
    list.splice(idx,1);
  }
  if (idx == 0){return list;}else{
      _remove(list,idx-1,predicated);
  }
}
//调用
var a = [1,2,3,4];
remove2(a,function(a){if (a == 3) return true; else return false;});
console.log(a); //[1,2,4]