JavaScript Learning Notes (unlike C + +)

1. After the new definition of the variable, the original data will not disappear. var x=3;var x; At this point, X is still 3.

2. If you assign a value to a variable that has not been declared, the variable is automatically declared as a global variable. For example, declare carname= "Volvo" within the function; At this point carname is the global variable.

3.for/in loops, which can be used to traverse the properties of an object

inperson)  {  txt=txt + person[x];  }

JavaScript Learning Notes (unlike C + +)