When you declare a variable, but don’t assign it a value, it will become undefined. This means that strict equality test will tell you, correctly, that these two are not the same. Undefined and null in JavaScript are different data types. Strict check will compare not only the value but also the data type. When you test for strict equality JavaScript doesn’t perform type coercion. Instead of loose equality, test for strict equality. If you want to avoid many problems, avoid testing for loose equality. The result of test for loose equality will result in match. Both, undefined and null, are falsy and this is what they will be considered. When you test for loose equality there is type coercion happening on the background. This is also why you should avoid testing for loose equality. One example of boolean context is condition in if…else statement. Boolean context is a context which evaluates to boolean value, either true or false. This means that when you use undefined in a boolean context it will be considered false. Another thing undefined and null have in common is that they are both falsy values. The rest of values in JavaScript are objects. These data types are Boolean, Number, String, Symbol, Null and Undefined. You will also learn what are some differences between these two and how to work with them.īoth, undefined and null, are primitive data types that exist in JavaScript. It will explain what undefined and null in JavaScript are. This tutorial will help you learn about them. Undefined and null are two data types in JavaScript that can sometimes be confusing.

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