Comparison

The operators

Comparison produces a boolean. Six of them matter, and this tutorial uses === and !== throughout for reasons the equality chapter covers.

console.log(5 === 5);
console.log(5 !== 3);
console.log(5 > 3);
console.log(5 < 3);
console.log(5 >= 5);
console.log(5 <= 4);

true
true
true
false
true
false

Comparing strings

The ordering operators work on strings too, comparing character by character using their code point. That is not alphabetical order.

console.log('apple' < 'banana');
console.log('Zebra' < 'apple');
console.log('10' < '9');

true
true
true

Capitals sort before lowercase, and digits compare as text, so the string "10" really is less than "9". For anything a person will read, use localeCompare:

const names = ['Zebra', 'apple', 'Banana'];

console.log(names.slice().sort());
console.log(names.slice().sort((a, b) => a.localeCompare(b)));

["Banana", "Zebra", "apple"]
["apple", "Banana", "Zebra"]

Mixed types

The ordering operators convert their operands to numbers first, which produces some odd but explainable results.

console.log('10' > 9);
console.log(true > 0);
console.log(null >= 0);
console.log(null > 0);

true
true
true
false

Comparing objects

Objects and arrays compare by identity, not contents. Two separately built objects are never equal, however alike they look.

const a = { id: 1 };
const b = { id: 1 };
const c = a;

console.log(a === b);
console.log(a === c);
console.log(JSON.stringify(a) === JSON.stringify(b));

false
true
true

The last line is a rough way to compare contents. It is fine for simple data and wrong for anything with functions, dates or a different key order.