在javascript中分配另一个键的值 [英] Assigning the value of another key in javascript

问题描述

我只想知道如何在同一个哈希中访问另一个键的值。哈希内部的
。不是通过做myHash.key2 = myHash.key1 ....;
我的意思是一种做法：

I would just like to know how to access the value of another key in the same hash. from inside the hash. not by doing myHash.key2 = myHash.key1....; I mean a way of doing :

var myHash = {
    key1: 5,
    key2: key1 * 7,
    key3: true,
    key4: (key3)? "yes" : "no"
};

PS：这只是实际代码的简化版本，实际上每个密钥都有一些复杂的操作。值而不是简单的数字或bools。

PS: this is only a simplified version of the actual code in fact every key has some complex operations inside. The values and not simple Numbers or bools.

推荐答案

您不能在文字定义中引用对象上的其他键。根据对象中的其他键或其他值设置键的选项包括：

You cannot refer to other keys on the object within a literal definition. The options for setting a key based on other keys or other values within the object are:

1. 使用键的getter函数可以根据其他属性返回值。

1. Use a getter function for the key that can return a value based on other properties.

使用常规函数作为可以根据其他属性返回值的键。

Use a regular function for the key that can return a value based on other properties.

在文字定义之外指定一个键/值，您可以根据其他键/属性分配静态值。

Assign a key/value outside of the literal definition where you can assign a static value based on the other keys/properties.

以下是每个选项的示例：

Here are examples of each of these options:

// use getters for properties that can base their values on other properties
var myHash = {
    key1: 5,
    get key2() { return this.key1 * 7; },
    key3: true,
    get key4() { return this.key3 ? "yes" : "no";}
};

console.log(myHash.key2);    // 35

// use regular functions for properties that can base 
// their values on other properties
var myHash = {
    key1: 5,
    key2: function() { return this.key1 * 7; },
    key3: true,
    key4: function() { return this.key3 ? "yes" : "no";}
};

console.log(myHash.key2());    // 35

// assign static properties outside the literal definition
// that can base their values on other properties
var myHash = {
    key1: 5,
    key3: true
};
myHash.key2 = myHash.key1 * 7;
myHash.key4 = myHash.key3 ? "yes" : "no";

console.log(myHash.key2);    // 35

注意：前两个选项是实时。如果更改 myHash.key1 的值，则 myHash.key2 或的值myHash.key2（）也会改变。第三个选项是static， myHash.key2 的值不会跟随 myHash.key1 中的更改。

Note: the first two options are "live". If you change the value of myHash.key1, then the value of myHash.key2 or myHash.key2() will change too. The third option is static and the values of myHash.key2 will not follow changes in myHash.key1.

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