Why Does '0' Equal False, But It's True When Tested with if in JavaScript?

JavaScript Equality Puzzle: "0" Is False, But It's True When Tested with if

JavaScript's equality operators can lead to unexpected results, as demonstrated by the following code:

console.log("0" == false); // true
console.log(false == "0"); // true

This code implies that the string "0" is equivalent to the Boolean value false. However, the following code prints "ha" despite the condition being "0":

if ("0") console.log("ha"); // ha

Why is this happening?

To understand this behavior, we need to understand JavaScript's truthy and falsy values. In JavaScript, the following values are falsy:

false
0
""
null
undefined
NaN

All other values are truthy.

In the first two lines of the code snippet, the equality operator (==) performs type coercion to compare the string "0" with the Boolean value false. Since "0" is a falsy value, it is considered equal to false.

However, the if statement in the third line of code uses strict equality (===), which only considers values of the same type as equal. Since "0" is a string and false is a Boolean, the condition is evaluated as false.

To avoid confusion, it is recommended to use strict equality (===) when comparing values in JavaScript. The following modified code will print "nothing":

if ("0" === false) console.log("ha"); // nothing

By understanding the difference between equality (==) and strict equality (===), you can write JavaScript code that accurately compares values.

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