JavaScript符号不会阻止对象中的名称冲突

Question

我已经开始在JavaScript中看看Symbols了,并且已经开始在我的Objects中使用它们来帮助解决名称冲突,但是在使用它时我仍然可以覆盖属性？我很难理解JavaScript中符号的含义.他们被说了很多,人们说他们很聪明,因为他们不会在对象中引起命名冲突,但我看不出怎么样？

    // Create your object
let obj = {};

// Create your Symbol
let address = Symbol("the address symbol");

// Assign your Symbol as a key to a value
obj[address] = "123 Bond street";

// Return '123 Bond street'
console.log(obj[address])


// Another dev comes along

// Assigns an address property to your object
obj[address] = "456 Regent street";

// Your address property has been overwritten?
console.log(obj[address])

据我所知,从我的代码中我仍然可以覆盖对象的属性？那么这个符号是如何帮助的呢？

我用错了吗？

Answer 1

您似乎认为每次访问address新的不同符号值时都会被分配,这是不正确的.

您所做的只是使用Symbol生成唯一值,然后将该值存储在address变量中.这意味着当您稍后再次使用它时,您使用的是之前生成的相同符号.即使您没有使用Symbol,情况也是如此:

let obj = {};   // Create your object
    
let address = "some key name";
obj[address] = "123 Bond street";  
console.log(obj[address]);  // Return '123 Bond street'
    
// Another dev comes along
obj[address] = "456 Regent street";   // Assigns an address property to your object
console.log(obj[address]);  // Your address property has been overwritten

简而言之,如果您存储符号,那么您只需存储一个保证唯一的值.但是,这并不能阻止你一遍又一遍地使用它.

更合适的用法Symbol是阻止另一个开发人员在现有对象上创建一个新密钥,其名称与从其他符号生成的密钥相同:

let obj = {};   // Create your object
    
let address = Symbol("some key name");
obj[address] = "123 Bond street";  
console.log(obj[address]);  // Return '123 Bond street'
    
// Another dev comes along
let newProp = Symbol("some key name");
obj[newProp] = "456 Regent street";   // Guaranteed unique new key is created

// There is no way the two properties would ever overwrite each other because each
// was created from a different Symbol
console.log(obj[address]);  
console.log(obj[newProp]);