ES2019 introduces the Array.prototype.flatMap method. In this lesson, we'll investigate a common use case for mapping and filtering an array in a single iteration. We'll then see how to do this using Array.prototype.reduce, and then refactor the code…
本文是笔者在看廖雪峰老师JavaScript教程时的个人总结 高阶函数 一个函数就接收另一个函数作为参数,这种函数就称之为高阶函数 1.高阶函数之map: 此时我们有一个数组和一个接受一个参数并返回一个数的函数.我们需要把这个数组的每一个值在这个函数上走一遍,从而得到一个新数组.此时就需要map了 var a = [1,2,3,4,5,6]; var b = [] var fu…
map将函数作用到数据集的每一个元素上,生成一个新的分布式的数据集(RDD)返回 map函数的源码: def map(self, f, preservesPartitioning=False): """ Return a new RDD by applying a function to each element of this RDD. >>> rdd = sc.parallelize(["b", "a", &q…
Both map and filter do not modify the array. Instead they return a new array of the results. Because both map and filter return Arrays, we can chain these functions together to build complex array transformations with very little code. Finally we can…