Baseline Widely available
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.
function getFee(isMember) {
return isMember ? "$2.00" : "$10.00";
}
console.log(getFee(true));
// Expected output: "$2.00"
console.log(getFee(false));
// Expected output: "$10.00"
console.log(getFee(null));
// Expected output: "$10.00"
condition ? exprIfTrue : exprIfFalse
condition
An expression whose value is used as a condition.
exprIfTrue
An expression which is executed if the condition evaluates to a truthy value (one which equals or can be converted to true).
exprIfFalse
An expression which is executed if the condition is falsy (that is, has a value which can be converted to false).
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.
const age = 26;
const beverage = age >= 21 ? "Beer" : "Juice";
console.log(beverage); // "Beer"
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"
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;
}
}
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