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 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.

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.

One common usage is to handle a value that may be null:

let greeting = person => {
    let 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;
}

// Equivalent to:

function example(…) {
    if (condition1) { return value1; }
    else if (condition2) { return value2; }
    else if (condition3) { return value3; }
    else { return value4; }
}

• if statement
• Nullish coalescing operator
• Optional chaining
• Making decisions in your code — conditionals
• Expressions and operators