The difference between == and === in JS is:
“==” is the equality operator, which checks if the values on both sides are equal after performing type coercion.
Type coercion means that if the operands are of different types, JavaScript will attempt to convert them to the same type before making the comparison.
“===” is the strict equality operator, which also checks if the values on both sides are equal but without performing type coercion.
Example:
console.log(5 == "5"); // true, because "5" is coerced to a number and then compared to 5
console.log(5 === "5"); // false, because the types are different
console.log(5 == 5); // true
console.log(5 === 5); // true
console.log(0 == false); // true, because false is coerced to 0
console.log(0 === false); // false, because they are of different typesWhat is Type Coercion in JavaScript and How Does It Work?
difference between == and === in JS
Type coercion in JavaScript refers to the automatic conversion of values from one data type to another when they are used in a context that requires a different type.
Type coercion often occurs implicitly, meaning that JavaScript automatically performs the conversion without requiring explicit instructions from the developer.
Implicit Type Coercion
difference between == and === in JS
Occurs when JavaScript automatically converts values from one type to another during operations like comparisons, arithmetic operations, or concatenations.
For example, when you use the “+” operator with a string and a number, JavaScript will convert the number to a string and concatenate them.
console.log("5" + 3); // "53", because 3 is coerced into a string and concatenated
console.log("5" - 3); // 2, because "5" is coerced into a number and then subtracted from 3
console.log("5" == 5); // true, because "5" is coerced into a number for comparisonExplicit Type Coercion
difference between == and === in JS
Occurs when you explicitly convert values from one type to another using built-in functions or operators like parseInt(), parseFloat(), Number(), String(), etc.
console.log(Number("5")); // 5, converts the string "5" to a number
console.log(String(5)); // "5", converts the number 5 to a stringWhen to use “==” (double equals) and “===” (triple equals)?
difference between == and === in JS
== | === | |
|---|---|---|
| Use for loose equality comparison when type coercion is acceptable | Use for strict equality comparison when strict type checking is required | |
Check for equality between different types when comparing against null or undefined | Ensure both value and type are identical |
Bottom Line
difference between == and === in JS
Double equals and triple equals are comparison operators.
Use == for loose equality comparisons when type coercion is acceptable, and use === for strict equality comparisons when you need to ensure both value and type are identical.
What to do next?
See Javascript Question #3: “What is event delegation in JS?“
