Sometimes you need to filter an array of objects or perform other conditional logic based on a combination of factors. Ramda's where function gives you a concise way to declaratively map individual predicates to object properties, that when combined,…

We don't always control the data we need in our applications, and that means we often find ourselves massaging and transforming our data. In this lesson, we'll learn how to transform objects in a declarative way using ramda's evolve function. Assume…

In this lesson we'll learn the basics of using lenses in Ramda and see how they enable you to focus changes on specific properties of an object while keeping your data immutable. what 'R.lens' do is able to get or set prop value but keep the object i…

一.spring Ioc容器补充(1) Spring Ioc容器 DI(依赖注入): 注入的方式:设值方法注入setter(属性注入)/构造子注入(构造函数传入依赖的对象)/字段注入field(注解)/接口注入out 装配的方式:手动装配<property>,<constructor-arg>,@Autowired,@Resource/自动装配 1.装配各种类型的属性: A.简单属性value属性或者value元素 <bean id="person" cl…

ES6 Map vs ES5 Object Map vs Object https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Map#Objects_vs._Maps Maps 和 Objects 的区别 键类型不同,一个 Object 的键只能是字符串或者 Symbols,但一个 Map 的键可以是任意值; 键顺序不同,Map 中的键值是有序的(FIFO 原则),而添加到对象中的键则不是…

In this lesson, we’ll use a Maybe to safely operate on properties of an object that could be undefined. We’ll use our initial code as the basis for a prop utility function that can be reused with different objects and various property names. Instead…

Use Maps when keys are unknown until runtime: Map: let recentPosts = new Map(); createPost( newPost, (data)=>{ // Key unknown until runtime, so use Map recentPosts.set(data.author, data.message); }); Object: const POST_PRE_PAGE=15; // Keys are previo…

private void sort(List<Map<String, Object>> list) { Collections.sort(list, new Comparator<Map<String, Object>>(){ public int compare(Map<String, Object> o1, Map<String, Object> o2) { //依据map中某个字段,从小到大排序 return (Integer)…

1.掌握Map接口中常用方法. 2.遍历Map集合的两种方式都要精通. 第一种:获取所有key,遍历每个key,通过key获取value. 第二种:获取Set<Map.Entry>即可,遍历Set集合中的Entry 调用entry.getKey() entry.getValue() 3.了解哈希表数据结构. 4.存放在HashMap集合key部分和HashSet集合中的元素需要同时重写hashCode和equals. 5.HashMap和Hashtable的区别. HashMap: 初始化容量…

In this lesson, we’ll look at the propPath utility function. We’ll ask for a property multiple levels deep in an object and get back a Maybe. We’ll get a Just when the property exists at our path and a Nothing if any part of the path is undefined. co…