Conditional (ternary) operator

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 followed by a colon (:), and finally the expression to execute if the condition is . This operator is frequently used as an alternative to an if...else statement.

Syntax

condition ? exprIfTrue : exprIfFalse

Parameters

condition
- : An expression whose value is used as a condition.
exprIfTrue
- : An expression which is executed if the condition evaluates to a value (one which equals or can be converted to true).
exprIfFalse
- : An expression which is executed if the condition is (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;
  }
}