在多個條件中使用？ ：javascript中的語句

Question

需要檢查三個條件並根據條件爲變量賦值。

if(a =="z1"){ 
    b = "one"; 
} else if(a =="z2"){ 
    b = "two"; 
} else if(a =="z3"){ 
    b = "three"; 
} 

是否可以在JavaScript中使用？ ：聲明使其成爲單行代碼

Answer 1

是的，您可以使用將其轉換爲Conditional(ternary) operator。

var a = "z3"; 
 
var b = a == "z1" ? "one" : a == "z2" ? "two" : a == "z3" ? "three" : "" ; 
 

 
console.log(b);

---

FYI：爲了更好的可讀性，我會建議使用 if...else語句或使用 switch聲明。儘管在複雜操作的情況下需要使用括號來嵌套三元運算符，以避免出現問題。

Answer 2

var b = (a =="z1") ? "one" : ((a =="z2") ?"two":(a =="z3")?"three":null); 

不要忘了，閱讀這篇文章很難。 如果使用一個if else塊，則可以使用。

Answer 3

你可以做這樣的事情：？？？

B =（A == 「Z1」， 「一個」 :(一== 「Z2」， 「二」 :(一== 「Z3」「三「：！未定義）））

Answer 4

var b = a == "z1" ? "one" : (a == "z2" ? "two" : (a == "z3" ? "three" : undefined)) ; 

a = "z1" 
 

 
alert(a == "z1" ? "one" : (a == "z2" ? "two" : (a == "z3" ? "three" : undefined))); 
 

 
a = "z2" 
 

 
alert(a == "z1" ? "one" : (a == "z2" ? "two" : (a == "z3" ? "three" : undefined))); 
 

 
a = "z3" 
 

 
alert(a == "z1" ? "one" : (a == "z2" ? "two" : (a == "z3" ? "three" : undefined))); 
 

 
a = "z4" 
 

 
alert(a == "z1" ? "one" : (a == "z2" ? "two" : (a == "z3" ? "three" : undefined)));