• ES6引入了3种编写对象字面量的方法
• 第一种方法：

- ES6 Enhanced object literal syntax can take an external object like salary object and make it a property of the developer object as shown below:
const salary = {
  fixed: '$200k',
  variable: '$100k'
}

const developer = {
  // salary: salary      // Before ES6
  salary                 // ES6 way
}

developer; // { salary: { fixed: '$200k', variable: '$100k' } }

- If any change is made in salary object, same change needs to be made inside the developer object for salary object which is present as property of developer object.

• 第二种方式：
• 我们不需要创建属性然后将其设置为函数表达式。我们可以直接编写而不需要 function 关键字，如下所示，即 ES6 方式。

const salary = {
  fixed: '$200k',
  variable: '$50k'
}

const developer = {
  salary,
  /* Before ES6
  greet: function(name){
    console.log(`Salary credited. Enjoy ${name}!`);
  }*/
  // ES6 Way
  greet(name){
    console.log(`Salary credited. Enjoy ${name}!`);
  }
}

developer.greet("Peter");

• 第三种方式：
• 属性名称也可以计算

const seasons = ['winter','summer','spring', 'monsoon','autumn'];

const fruits = {
  [seasons[0]]: 'apple',
  [seasons[1]]: 'mango',
  [[seasons.length]]: 'cherry'
}

fruits;   // { '5': 'cherry', winter: 'apple', summer: 'mango' }