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Starting with JavaScript 1.5, ISO 8859-1 or Unicode letters (or \uXXXX Unicode escape sequences) can be used in identifiers.cite-ref-6[6] In certain JavaScript implementations, the at sign (@) can be used in an identifier, but this is contrary to the specifications and not supported in newer implementations.

Variables declared with var are lexically scoped at a function level, while ones with let or const have a block level scope. Since declarations are processed before any code is executed, a variable can be assigned to and used prior to being declared in the code.cite-ref-7[7] This is referred to as hoisting, and it is equivalent to variables being forward declared at the top of the function or block.cite-ref-8[8]

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