Hoisting is Pre-Scope in JavaScript. Only declarations themselves are hoisted, while assignments not.
\nFor Expample-<\/p>\n
exp();\r\n\r\nfunction exp(){\r\n console.log(a);\r\n var a=1;\r\n}\r\n<\/pre>\nIn above code snippet there will be no error but the output will be undefined because JavaScript see this code as-<\/p>\n
function exp(){\r\n var a;\r\n console.log(a);\r\n a=2;\r\n}\r\nexp();\r\n<\/pre>\nThe declaration comes first and then assignment comes. Js Engine compile JS code before it interprets.
\nCompilation phase has to find associate all declarations with their appropriate scopes.
\nLike you think var a=1; as one statement while JS thinks it as two like-<\/p>\n
var a; \/\/ compilation phase\r\na=1; \/\/ execution phase<\/pre>\nNow we will take another example-<\/p>\n
exp();\r\nvar exp= function abc(){\r\n};<\/pre>\nIt will not throw the reference error but it has no value yet. So exp() is trying to invoke undefined value which is TypeError.
\nLets take one more example-<\/p>\n
exp();\r\nabc();\r\nvar exp= function abc() {};\r\n<\/pre>\nIt will interpret as-<\/p>\n
var exp;\r\nexp();\r\nabc();\r\n\r\nexp = function(){\r\n var abc= --self--\r\n}\r\n\/\/ Uncaught TypeError: exp is not a function\r\n<\/pre>\n