测试是否定义了变量，如果没有定义，请在Coffeescript中为它分配一个空字符串？

Question

Here is my coffeescript code:

if c.urls.voice then c.urls.voice else ""

Does anyone have any ideas about whether there is a better way to write this code in Coffeescript?

Answer 1

Just use the existential operator to assign to a non-existing variable/property:

c.urls.voice ?= ""

Alternatively, if you don't want to assign it but only access with a default value, use the or (or || ) operator:

… = c.urls.voice or "" // equivalent to your if statement

however I guess you're even here actually looking for the existential operator which specifically checks for null and undefined values, not all falsy ones:

… = c.urls.voice ? ""

Answer 2

I found this works for me:

c.urls.voice ? ""

which will compiles into:

var _ref;

if ((_ref = c.urls.voice) != null) {
  _ref;
} else {
  "";
};