javascript - How does a variable without var keyword in self invoking function works? -

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• surprised global variable has undefined value in javascript 4 answers

var salary = "1000$";  (function () {     console.log("original salary " + salary); //1000$      salary = "5000$";      console.log("my new salary " + salary); //5000$ })();  (function () {     console.log("original salary " + salary); //undefined ??       var salary = "5000$";      console.log("my new salary " + salary); //5000$ })(); 

why , how first , third console logs displaying different outputs ?

this due variable hosting .in second iife function , have declared salary variable , moves top of function , overshadows global salary function

javascript convrts code .see code.

  var salary = "1000$";      (function () {         console.log("original salary " + salary); //1000$          salary = "5000$";          console.log("my new salary " + salary); //5000$     })();      (function () {         var salary ;         console.log("original salary " + salary); //undefined ??           // move opvar salary = "5000$";         salary = "5000$";          console.log("my new salary " + salary); //5000$     })();