JS 拷贝：浅拷贝 / 深拷贝原理 + 常用方法

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The URL Pattern API defines a syntax that is used to create URL pattern matchers. These patterns can be matched against URLs or individual URL components.

深拷贝和浅拷贝的区别？ 浅拷贝：将原对象或原数组的引用直接赋给新对象，新数组，新对象／数组只是原对象的一个引用。 深拷贝：创建一个新的对象和数组，将原对象的各项属性的“值”（数组的所有元素）拷贝过来，是“值”而不是“引用”。 为什么要用深拷贝？ 我们希望在改变新的数组（对象）的时候，不改变原数组（对

This article briefly introduces databases, and how to use them with Node/Express apps. It then goes on to show how we can use Mongoose to provide database access for the LocalLibrary website. It explains how object schema and models are declared, the main field types, and basic validation. It also briefly shows a few of the main ways in which you can access model data.

js中对于基本类型数据的拷贝(复制)就是值本身，而对于引用类型数据，则分为深拷贝和浅拷贝。 浅拷贝 js对象浅拷贝：拷贝的是其引用地址，也就是说，如果原地址中对象被改变了， 那么浅拷贝出来的对象也会相应改变letobj1 = {a:1};letobj2 = obj1; obj2.a = 2;

简单来说，深拷贝主要是将另一个对象的属性值拷贝过来之后，另一个对象的属性值并不受到影响，因为此时它自己在堆中开辟了自己的内存区域，不受外界干扰。 浅拷贝主要拷贝的是对象的引用值，当改变对象的值，另一个对象的值也会发生变化。 1.简单深拷贝(一层浅拷贝) ①for循环拷贝 ②Object.assign

In this tutorial we'll set up routes (URL handling code) with "dummy" handler functions for all the resource endpoints that we'll eventually need in the LocalLibrary website. On completion we'll have a modular structure for our route handling code, which we can extend with real handler functions in the following articles. We'll also have a really good understanding of how to create modular routes using Express!