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Undefined

undefined is a {{Glossary("primitive")}} value automatically assigned to {{glossary("variable", "variables")}} that have just been declared, or to formal {{Glossary("Argument","arguments")}} for which there are no actual arguments.

Example​

let x; //create a variable but assign it no value

console.log(`x's value is ${x}`); //logs "x's value is undefined"

See also​