# Undefined value

The value `undefined` denotes uncertainty. A variable will have such a value if we declared it, but did not write the value to it:

`let a; alert(a); // shows undefined`

This value can be assigned explicitly to a variable :

`let a = undefined; alert(a); // shows undefined`

Declare a variable without assigning a value to it. Display the value of the created variable on the screen.

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