Learn to love the === operator in JavaScript

In JavaScript there are two types of equality operator, the === and the !== , sorry I forgot to mention their evil twin == and != .

tsdr; (too short didn’t read) Use three equals unless you fully understand the conversions that take place for two-equals.

Basically what the triple equal (===) compares is if the value is equal and if the type is equal.

Lets look at an example below.

true == 1; //true, because 'true' is converted to 1
"1" == 1; //again true

true === 1 //false
"2" === 2 //false

true == 1; //true, because 'true' is converted to 1

"1" == 1; //again true

true === 1 //false

"2" === 2 //false

The reason for the === operator to return false is due to the fact that it does not do type coercion, but the double == does type coercion and implicitly tries to convert the value before comparing.

Some additional examples:

var x = [1,2,3];
var y = [1,2,3];
var z = x;

alert(x === y); // false (even though x and y are the same type)
alert(x === z); // true

var str1 = "ab" + "c";
var str2 = "abc";

alert(str1 === str2); // returns true, because strings behave like value types

var a = new String("123");
var b = "123";

alert(a === b); // returns false !! (but they are equal and of the same type)

var x = [1,2,3];

var y = [1,2,3];

var z = x;

alert(x === y); // false (even though x and y are the same type)

alert(x === z); // true

var str1 = "ab" + "c";

var str2 = "abc";

alert(str1 === str2); // returns true, because strings behave like value types

var a = new String("123");

var b = "123";

alert(a === b); // returns false !! (but they are equal and of the same type)

I hope the examples above give you the reason to stop using == and != since it convert things for you during comparison. So start using the triple === and !== .

Below are two tables that show the equality of == and === provide by http://dorey.github.io/JavaScript-Equality-Table/

x == y

x === y

Learn to love the === operator in JavaScript

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Learn to love the === operator in JavaScript

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