Sayangnya JavaScript tidak menyediakan cara yang sangat singkat dan mudah dibaca untuk melakukan ini. Secara pribadi saya hanya akan menggunakan beberapa pernyataan if baris tunggal seperti ini:
var inputOneAns;
if [inputOne === 'Yes'] inputOneAns = '517';
if [inputOne === 'No'] inputOneAns = '518';
else inputOneAns = '';
Yang bahkan bisa lebih bersih jika Anda abstrak menjadi fungsi [catatan: tidak perlu else dalam kasus ini]:
function getInputOneAns[inputOne] {
if [inputOne === 'Yes'] return '517';
if [inputOne === 'No'] return '518';
return '';
}
Secara pribadi, saya tidak begitu suka pernyataan pergantian karena ini karena dua alasan: pertama pernyataan ekstra break yang membengkak kode, dan
kedua, pernyataan pergantian sangat membatasi - Anda hanya dapat melakukan pemeriksaan kesetaraan sederhana, dan hanya terhadap satu variabel. Selain itu, jika Anda tahu Anda akan selalu memeriksa satu string, saya akan menyukai objek peta sederhana:
var map = { 'Yes': '517', 'No': '518' };
var inputOneAns = map[inputOne] || '';
The conditional [ternary] operator is the only JavaScript operator that takes three operands: a condition followed by a question mark [?], then an expression to execute if the condition is truthy followed by a colon [:], and finally the expression to execute if the condition is
falsy. This operator is frequently used as an alternative to an if...else statement.
Try it
Syntax
condition ? exprIfTrue : exprIfFalse
Parameters
condition
An expression whose value is used as a condition.
exprIfTrueAn expression which is executed if the condition evaluates to a truthy value [one
which equals or can be converted to true].
exprIfFalseAn expression which is executed if the condition is falsy [that is, has a value which can be converted to false].
Description
Besides false, possible falsy expressions are: null, NaN, 0, the empty string [""], and undefined. If condition is any of these, the result of the conditional expression will be the result of executing the expression exprIfFalse.
Examples
A simple example
const age = 26;
const beverage = age >= 21 ? "Beer" : "Juice";
console.log[beverage]; // "Beer"
Handling null values
One common usage is to handle a value that may be null:
const greeting = [person] => {
const name = person ? person.name : "stranger";
return `Howdy, ${name}`;
}
console.log[greeting[{ name: "Alice" }]]; // "Howdy, Alice"
console.log[greeting[null]]; // "Howdy, stranger"
Conditional chains
The ternary operator is right-associative, which means it can be "chained" in the following way, similar to an if … else if … else if … else chain:
function example[] {
return condition1 ? value1
: condition2 ? value2
: condition3 ? value3
: value4;
}
This is equivalent to the following
if...else chain.
function example[] {
if [condition1] {
return value1;
} else if [condition2] {
return value2;
} else if [condition3] {
return value3;
} else {
return value4;
}
}
Specifications
| ECMAScript Language Specification # sec-conditional-operator |
Browser compatibility
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