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
- 关于 JavaSrcipt 前端开发的建议：模块化开发
JavaScript 是一种优秀的脚本语言. 在 JavaScript 的诞生之初,便于 浏览器 密不可分,如今它更是到了服务器中大展身手. 但是这里不叙述服务端的开发建议. Script 翻译过来就 ...
- python3中的继承和多态
*继承 当我们定义一个class的时候,可以从某个现有的class继承,新的class称为子类(Subclass),而被继承的class称为基类.父类或超类(Base class.Super clas ...
- 关于C语言数组的小练习--笔记
#include <stdio.h> #include <windows.h> #include <mmsystem.h> #include <string. ...
- lua学习之复习汇总篇
第六日笔记 1. 基础概念 程序块 定义 在 lua 中任何一个源代码文件或在交互模式中输入的一行代码 程序块可以是任意大小的 程序块可以是一连串语句或一条命令 也可由函数定义构成,一般将函数定义写在 ...
- postman之设置关联
接口关联(上一个接口的返回参数作为下一个接口的入参使用): 一:在第一个接口的test点击Response body:JSON value check和set an environment varia ...
- tensorboard的简单使用
1. 首先保证你已有程序,下面是MLP实现手写数字分类模型的代码实现. 不懂的可以对照注释理解. #输入数据是28*28大小的图片,输出为10个类别,隐层大小为300个节点 from tensorfl ...
- 【WPF学习】第四十七章 WriteableBitmap类
WPF允许使用Image元素显示位图.然而,按这种方法显示图片的方法完全是单向的.应用程序使用现成的位图,读取问题,并在窗口中显示位图.就其本身而言,Image元素没有提供创建和编辑位图信息的方法. ...
- VFP9.0的GDI+类的使用
GDI+你应该不会陌生吧,然而,在VFP里要使用这一技术,可不是一件容易的事,你得学习一大堆API函数.或许,一想到这,你已经望而却步了.不过,从现在起,这一技术不再是豪门旺族的专宠了,我们每一位Fo ...
- FastDFS 配置文件 tracker.conf
FastDFS 版本5.05 配置文件分为三部分 控制器:tracker.conf存储器:storage.conf 客户端:client.conf 文件位置:/etc/fdfs 基本配置(基础配置 ...
- Tomcat 配置2 tomcat-users.xml
Tomcat的配置 Tomcat的主要配置文件有3个,分别是: Tomcat-users.xml. web.xml server.xml. 配置Tomcat-users.xml 该文 ...