Programming Tutorials

(追記) (追記ここまで)

Boolean() function in JavaScript

By: Stella in Javascript Tutorials on 2023年04月25日 [フレーム]

The Boolean() function in JavaScript is used to convert a value into a boolean data type. The function takes a single parameter and returns true or false.

The function can be called in two ways: with the new operator or without it. If called with the new operator, it creates a new Boolean object. If called without the new operator, it returns a boolean primitive.

When the parameter is a primitive value, the function returns true for truthy values and false for falsy values. The following values are considered falsy in JavaScript:

false
0 (zero)
"" (empty string)
null
undefined
NaN (Not-a-Number)

All other values are considered truthy.

Here are some examples:

Boolean(true); // true
Boolean(false); // false
Boolean(0); // false
Boolean(1); // true
Boolean(""); // false
Boolean("hello"); // true
Boolean(null); // false
Boolean(undefined);// false
Boolean(NaN); // false

It's important to note that the Boolean() function is not the same as the boolean keyword in JavaScript. The boolean keyword is used to declare a variable as a boolean data type, while the Boolean() function is used to convert a value into a boolean data type.

Previous
<< Template literals vs String concatenation in JavaScript

Next
Symbol() function in JavaScript>>

(追記) (追記ここまで)