``` >>> var a = 1; undefined >>> var result = ''; undefined >>> if(a === 1){ ... result = 'a is one'; ... }else{ ... result = 'a is not one'; ... } a is one ``` 将上面代码简化： ``` >>> var a = 1; undefined >>> var result = (a === 1) ? 'a is one' : 'a is not one'; undefined >>> result a is one ``` 这种运算符只用于一些特别简单的条件逻辑。别滥用，会让代码难以理解。