``` >>> var a = 1; undefined >>> var result = ''; undefined >>> if(a === 1){ ... result = 'a is one'; ... }else{ ... result = 'a is not one'; ... } a is one ``` 將上面代碼簡化： ``` >>> var a = 1; undefined >>> var result = (a === 1) ? 'a is one' : 'a is not one'; undefined >>> result a is one ``` 這種運算符只用于一些特別簡單的條件邏輯。別濫用，會讓代碼難以理解。