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Truthy and Falsy Values

Wherever JavaScript expects a boolean, you can provide any kind of value and it is automatically converted to boolean. Thus, there are two sets of values in JavaScript: one set is converted to false, while the other set is converted to true. These sets are called falsy values and truthy values. Given the preceding table, the following are all falsy values:

From

Cover of Speaking JavaScript

Note

truthy and falsy