zoukankan      html  css  js  c++  java
  • [Javascript] Querying an Immutable.js Map()

    Learn how to query an Immutable.Map() using get, getIn, has, includes, find, first and last. These are powerful operators that make finding data in an object graph pain free.

    has, includes, contains:

    //has()
    var map = Immutable.Map({a: '10'});
    console.log(map.has("a")); //true
    
    //includes / contains
    var todo = {
      id: +new Date(),
      name: "name",
      content: "content"
    };
    var todo2 = {
      id: +new Date(),
      name: "name",
      content: "content"
    };
    
    var todos = Immutable.Map();
    todos = todos.set(todo.id, todo);
    console.log(todos.contains(todo)); //true
    console.log(todos.contains(todo2)); //false

    first(), getIn()

    // first(), getIn()
    
    //Create tow Maps
    var todos = Immutable.Map();
    var todos2 = Immutable.Map();
    
    //Create new Data
    var todo1 = {
      id: +new Date(),
      name: "name",
      content: "content"
    };
    var todo2 = {
      id: +new Date()+1000,
      name: "name",
      content: "content"
    };
    var todo3 = {
      id: +new Date()+3000,
      name: "name",
      content: "content"
    };
    var todo4 = {
      id: +new Date()+4000,
      name: "name",
      content: "content"
    };
    
    //Add data to the map
    todos =todos.set(todo1.id, todo1);
    todos= todos.set(todo2.id, todo2);
    todos2=todos2.set(todo3.id, todo3);
    todos2=todos2.set(todo4.id, todo4);
    
    //Wrap maps in another map
    var multipleTodoStates = Immutable.Map({
        "todo1": todos,
        "todo2": todos2
    });
    
    //Get first todo's id in the first map
    const todoID = todos.first().id; 
    console.log(todoID);
    //Try to find the first todo in deep map
    //"todo1" is the first level map
    //then downto the second level to find the id
    //If nohting return null
    var res = multipleTodoStates.getIn(["todo1", todoID], null);
    var res2 = multipleTodoStates.getIn(["todo2", todoID], null);
    console.log(res);
    console.log(res2);

    find():

    //find()
    var todo = {
      id: +new Date(),
      name: "Wan",
      content: "Finish it"
    };
    
    var todos = Immutable.Map();
    todos = todos.set(todo.id, todo);
    
    var foundTodo = todos.find( (t)=>{
      return t.id === todo.id 
    }, null, null) ;
    
    console.log(foundTodo.id);
  • 相关阅读:
    公司后台切图
    XMLHttpRequest对象
    XML/JSDOM处理
    js访问xml之节点操作
    CSS3 输入框阴影效果及其他阴影效果
    GitHub用户仓库批量下载
    WTL10_9163应用向导安装后的小问题
    别学MFC了,要学就学这些...
    使用基于范围的 for 循环迭代范围
    使用未命名的命名空间代替静态全局变量
  • 原文地址:https://www.cnblogs.com/Answer1215/p/4890099.html
Copyright © 2011-2022 走看看