wat/docs/js/boolean/index.detail.md

Community-controlled cheat sheets for every coder.

## Boolean([value])

The `Boolean` object is an object wrapper for a boolean value.

The value passed as the first parameter is converted to a boolean value, if necessary. If value is omitted or is `0`, `-0`, `null`, `false`, `NaN`, `undefined`, or the empty string (`""`), the object has an initial value of `false`. All other values, including any object or the string `"false"`, create an object with an initial value of `true`.

Do not confuse the primitive `Boolean` values `true` and `false` with the `true` and `false` values of the `Boolean` object.

Any object whose value is not `undefined` or `null`, including a `Boolean` object whose value is `false`, evaluates to true when passed to a conditional statement. For example, the condition in the following if statement evaluates to `true`:

```js
var x = new Boolean(false);
if (x) {
  // this code is executed
}
```
This behavior does not apply to `Boolean` primitives. For example, the condition in the following `if` statement evaluates to `false`:

```js
var x = false;
if (x) {
  // this code is not executed
}
```

Do not use a `Boolean` object to convert a `non-boolean` value to a `boolean` value. Instead, use `Boolean` as a function to perform this task:

```js
var x = Boolean(expression);     // preferred
var x = new Boolean(expression); // don't use
```

If you specify any `object`, including a `Boolean` object whose value is `false`, as the initial value of a `Boolean` object, the new `Boolean` object has a value of `true`.

```js
var myFalse = new Boolean(false);   // initial value of false
var g = new Boolean(myFalse);       // initial value of true
var myString = new String('Hello'); // string object
var s = new Boolean(myString);      // initial value of true
```

Do not use a `Boolean` object in place of a `Boolean` primitive.