lodash fp.merge 为什么返回的是一个对象

Question

var fp = _.noConflict();
    console.log(fp.merge([],[]))
    console.log(_.merge([],[]))

为什么函数是编程的方法行为和正常的不一样，当合并两个数组的时候函数式编程的库返回的是一个对象

Answer 1

看下源码，merge调用的是createAssigner方法，该方法返回一个对象。

function createAssigner(assigner) {
  return (object, ...sources) => {
    let index = -1
    let length = sources.length
    let customizer = length > 1 ? sources[length - 1] : undefined
    const guard = length > 2 ? sources[2] : undefined

    customizer = (assigner.length > 3 && typeof customizer === 'function')
      ? (length--, customizer)
      : undefined

    if (guard && isIterateeCall(sources[0], sources[1], guard)) {
      customizer = length < 3 ? undefined : customizer
      length = 1
    }
    object = Object(object)
    while (++index < length) {
      const source = sources[index]
      if (source) {
        assigner(object, source, index, customizer)
      }
    }
    return object
  }
}