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JavaScript Comparisons

Ask If One Thing Equals Another

JavaScript Comparisons

Compare values with `===`, `!==`, `<`, `>`, `<=`, `>=`. Always use strict equality.

4 min read Level 1/5 #comparisons#equality#operators
What you'll learn
  • Use `===` and `!==` for equality
  • Compare numbers and strings with `<`, `>`, `<=`, `>=`
  • Avoid `==` and its silent type coercion

Comparison operators ask “how does this value compare to that one?” They return a boolean — either true or false.

The six comparison operators script.js 
console.log(5 === 5);   // true
console.log(5 !== 6);   // true
console.log(5 > 3);     // true
console.log(5 < 3);     // false
console.log(5 >= 5);    // true
console.log(5 <= 4);    // false
▶ Preview: console

Always Use ===

You’ll see two equality operators in JavaScript code:

  • “=== strict equality — compares value AND type”
  • == loose equality — converts types before comparing

Use ===. Always. The loose version has surprising results that nobody remembers correctly.

Strict vs loose script.js 
console.log(5 === "5");   // false   ← strict: different types
console.log(5 == "5");    // true    ← loose: converts the string

console.log(0 == "");     // true    ← surprising
console.log(0 == false);  // true    ← surprising
console.log(null == undefined); // true   ← surprising
▶ Preview: console

Comparing Strings

Strings compare lexicographically — character by character, by their Unicode code points.

String comparison script.js 
console.log("apple" < "banana");  // true
console.log("Apple" < "apple");   // true  ← capitals sort first
console.log("10" < "9");          // true  ← "1" < "9" as strings
▶ Preview: console

For human-friendly comparisons (alphabetical, case-insensitive, locale-aware), use localeCompare:

localeCompare script.js 
console.log("Apple".localeCompare("apple"));
// 1 (or -1 in some locales) — handles case + accents per locale
▶ Preview: console

Comparing Different Types

Mixing types in comparisons with < / > triggers conversion to numbers. It works, but the result is often a surprise.

Mixed-type comparisons script.js 
console.log("5" < 10);    // true   ← "5" converted to 5
console.log("abc" < 10);  // false  ← "abc" becomes NaN
console.log("abc" > 10);  // false  ← NaN comparisons are all false
▶ Preview: console

Stay safe by comparing values of the same type.

NaN Doesn’t Compare With Itself

NaN comparisons script.js 
console.log(NaN === NaN);  // false
console.log(NaN < 1);      // false
console.log(NaN > 1);      // false
console.log(Number.isNaN(NaN)); // true ← the correct check
▶ Preview: console

Up Next

Now that you can ask questions about values, time to act on the answers. if/else.

JavaScript If/Else →