javascript - 以下脚本中的 'foo'和 'bar'是什么，需要定义吗？

Question

只是一个示例代码:

  function process(elements) {
    var total = 0;
    for (i = 0; i < elements.length; i++) {
      if (elements[i].value) {
        total++;
      }
    }
    if (total) {
      return {
        foo: 'Wow!'
      };
    } else {
      return {
        foo: 'Great!',
        bar: 'Bravo!'
      };
    }
  }

foo 和 bar 是否称为属性？它们是否需要声明，例如:

var foo;
var bar;

Answer 1

像这样的线条

  return {
    foo: 'Great!',
    bar: 'Bravo!'
  };

正在返回 object这是使用 initializer notation 即时初始化的.

Objects can be initialized using new Object(), Object.create(), or using the literal notation (initializer notation). An object initializer is a comma-delimited list of zero or more pairs of property names and associated values of an object, enclosed in curly braces ({}).

所以 foo 和 bar 是属性名，因此不需要用 var 声明。

The terms foobar (/ˈfuːbɑːr/), or foo and others are used as placeholder names (also referred to as metasyntactic variables) in computer programming or computer-related documentation.[1] They have been used to name entities such as variables, functions, and commands whose exact identity is unimportant and serve only to demonstrate a concept.

您可以在 wikipedia 上阅读更多关于历史和词源的信息.