使用CoffeeScript检查对象中是否存在密钥的最简单方法

In CoffeeScript, what is the simplest way to check if a key exists in an object?

在CoffeeScript中，检查对象中是否存在密钥的最简单方法是什么？

3 个解决方案

#1

176

key of obj

This compiles to JavaScript's key in obj. (CoffeeScript uses of when referring to keys, and in when referring to array values: val in arr will test whether val is in arr.)

这将编译为obj中的JavaScript键。（CoffeeScript在引用键时使用，在引用数组值时：arr中的val将测试val是否在arr中。）

thejh's answer is correct if you want to ignore the object's prototype. Jimmy's answer is correct if you want to ignore keys with a null or undefined value.

如果你想忽略对象的原型，那么你的答案是正确的。如果要忽略具有null或未定义值的键，Jimmy的答案是正确的。

#2

The '?' operator checks for existence:

'？'操作员检查是否存在：

if obj?
    # object is not undefined or null

if obj.key?
    # obj.key is not undefined or null

# call function if it exists
obj.funcKey?()

# chain existence checks, returns undefined if failure at any level
grandChildVal = obj.key?.childKey?.grandChildKey

# chain existence checks with function, returns undefined if failure at any level
grandChildVal = obj.key?.childKey?().grandChildKey

#3

obj.hasOwnProperty(name)

(to ignore inherited properties)

（忽略继承的属性）

#1

176

key of obj