Travase Objects and four method of array
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Title</title>
</head>
<body>
<script>
var iterableObj = {
"lastName":'luo',
"firstName":'xu',
"age":19
}
let keys = Object.keys(iterableObj); //return array of keys in the iterableObj
// console.log(keys) //Array(3) [ "lastName", "firstName", "age" ]
let vals = Object.values(iterableObj);
//console.log(vals) //["luo","xu",19]
let entries = Object.entries(iterableObj)
//console.log(entries) //[["lastName", "luo"],[ "firstName", "xu"],["age", 19]] 2-D arrays
const companies = [ //array
{name: "Company One", category: "Finance", start: 1981, end: 2003}, //object
{name: "Company Two", category: "Retail", start: 1992, end: 2008},
{name: "Company Three", category: "Auto", start: 1999, end: 2007},
{name: "Company Four", category: "Retail", start: 1989, end: 2010},
{name: "Company Five", category: "Technology", start: 2009, end: 2014},
{name: "Company Six", category: "Finance", start: 1987, end: 2010},
{name: "Company Seven", category: "Auto", start: 1986, end: 1996},
{name: "Company Eight", category: "Technology", start: 2011, end: 2016},
{name: "Company Nine", category: "Retail", start: 1981, end: 1989}
];
const ages = [33, 12, 20, 16, 5, 54, 21, 44, 61, 13, 15, 45, 25, 64, 32];
//1. forEach()
for (let i = 0; i < companies.length; i++){
// console.log(companies[1]);
}
companies.forEach(function (company, index , companies) { //we can pass 2 params
// console.log(company);
});
//2. filter()
//store the person'age over 21, who can drink
var canDrink = [];
for (let i=0; i< ages.length ; i++){
if (ages[i] >= 21){
canDrink.push(ages[i]);
}
}
canDrink = ages.filter(function (age) {
if (age >= 21){
return true;
}
});
canDrink = ages.filter(age => age >=21);
console.log(canDrink);
//get companies that lasted ten years or more
const lastedTenYears = companies.filter((company, index) => (company.end - company.start >=10));
console.log(lastedTenYears);
//3. map()
var testMap = companies.map(function (company,index ) {
return company.name;
}); //Array(9) [ "Company One", "Company Two", "Company Three", "Company Four", "Company Five", "Company Six", "Company Seven", "Company Eight", "Company Nine" ]
testMap = companies.map(function (company ) {
return `${company.name } [${company.end} - ${company.start}]`;
}) //Array(9) [ "Company One [2003 - 1981]", "Company Two [2008 - 1992]", "Company Three [2007 - 1999]", "Company Four [2010 - 1989]", "Company Five [2014 - 2009]", "Company Six [2010 - 1987]", "Company Seven [1996 - 1986]", "Company Eight [2016 - 2011]", "Company Nine [1989 - 1981]" ]
console.log(testMap)
//4. sort()
//sort by start year
var sorted = companies.sort(function (a,b ) {
if (a.start > b.start){
return 1;
}else {
return -1;
}
});
sorted = companies.sort((a,b) => a >b ? 1 : -1);
//sort ages
sorted =ages.sort((a,b) => a-b);
console.log(sorted);
//5. reduce()
var total = ages.reduce(function (total, age) {
return total+age;
});
total = ages.reduce((total, age) => total +age);
console.log(total);
</script>
</body>
</html>
Travase Objects and four method of array的更多相关文章
- Why does typeof array with objects return “Object” and not “Array”?
https://stackoverflow.com/questions/4775722/check-if-object-is-an-array One of the weird behaviour a ...
- OBJC运行时方法替换(Method swizzling)
在上周associated objects一文中,我们开始探索Objective-C运行时的一些黑魔法.本周我们继续前行,来讨论可能是最受争议的运行时技术:method swizzling. Me ...
- iOS 判断数组array中是否包含元素a，取出a在array中的下标+数组方法详解
目前找到来4个解决办法,第三个尤为简单方便 NSArray * arr = @["]; //是否包含 "]) { NSInteger index = [arr indexOfObj ...
- JavaScript : Array assignment creates reference not copy
JavaScript : Array assignment creates reference not copy 29 May 2015 Consider we have an array var a ...
- matlab中cell array的理解
1. matlab中有一个函数iscell() 用于判断一个数组是不是cell array 参考:MATLAB Function Reference iscell Determine whether ...
- JavaScript Array.map
Array.prototype.map() History Edit This article is in need of a technical review. Table of Contents ...
- Design Pattern ->Factory Method
Layering & Contract Philosophy With additional indirection Factory Method The example code is as ...
- JavaScript 中Array数组的几个内置函数
本文章内容均参考<JavaScript高级程序设计第三版> 今天在看JavaScript书籍的时候,看到之前没有了解过的JavaScript中Array的几个内置函数对象,为了之后再开发工 ...
- ios method swizzling
阅读器 iOS开发iOS 本文由TracyYih[博客]翻译自NSHipster的文章Method Swizzling. 在上周associated objects一文中,我们开始探索Ob ...
随机推荐
- JDK源码系列总索引
一 目标 记录学习jdk源码的一些笔记和心得,jdk版本使用11.0.1,工具idea Class后面序号为优先级1-4,优先级递减 目录转载自博客: https://blog.csdn.net/qq ...
- Linux(Centos)安装tomcat并且部署Java Web项目
步骤一.下载安装包 a. 下载tomcat linux安装包,地址:http://tomcat.apache.org/download-80.cgi , 我们下载的版本是8.0,下载方式如图: b ...
- JSP-导入taglib 出现classNotFound异常
案例 前端登录跳转到指定jsp,报classNoFoundException,原因是页面导入 <%@ taglib uri="http://java.sun.com/jsp/jstl/ ...
- 线程池之 Executors
线程池之 Executors + 面试题 线程池的创建分为两种方式:ThreadPoolExecutor 和 Executors,上一节学习了 ThreadPoolExecutor 的使用方式,本节重 ...
- 给定区间[-2的31次方, 2的31次方]内的3个整数A、B和C，请判断A+B是否大于C
题目描述给定区间[-2的31次方, 2的31次方]内的3个整数A.B和C,请判断A+B是否大于C. 输入描述:输入第1行给出正整数T(<=10),是测试用例的个数.随后给出T组测试用例,每组占一 ...
- 关于android 中WebView使用Css
demo private static final String linkCss = "<link rel=\"stylesheet\" href=\"f ...
- List<E> 、Set<E>和Map<K,E>的简单应用
题目一: 创建两个线性表,分别存储{“chen”,“wang”,“liu”,“zhang”}和{“chen”,“hu”,“zhang”},求这两个线性表的交集和并集. 代码: List_Test.ja ...
- 1276:【例9.20】P2758 编辑距离
题目传送门[(https://www.luogu.com.cn/problem/P2758)] 题目描述 设A和B是两个字符串.我们要用最少的字符操作次数,将字符串A转换为字符串B.这里所说的字符操作 ...
- 《自拍教程5》Python自动化测试学习思路
前提:熟悉测试业务及流程 任何Python自动化测试的前提,都是必须先熟悉实际测试业务. 任何脱离实际测试业务的自动化都是噱头且无实际意义! 测试的基本流程基本是: 测试需求分析,测试用例设计与评审, ...
- linux shell实用常用命令
本文主要介绍Linux Shell的一些使用小技巧收集,非常实用,需要的朋友可以参考下. 查看本机某端口是否被占用 netstat -anpt | grep 22 查看远程某端口是否被开放 echo ...