Data type, operator

• Six types of data: object, string, null, Undefined, boolean, number;
  • Any data type + "" will be converted into a string;
  • null and undefined Although both are empty, null typeof is Object,undefined typeof is undefined;
  • Number conversion has pareseint and Paresefloat two, the former is converted to integers, the latter is the conversion is a decimal, but they in the parsing of numbers and strings, encountered a string will terminate parsing;
  • var num = 1.2345;num2 = num.tofixed (2);//will save two digits after the decimal point
  • Boolean True and False when the operation is true, the return of 1,false is 0;
• Operators include: arithmetic character +-*/,++--; logical character && | | <><=>= = = = = = = = = equals! = Not equal to
  • The difference between a++ and ++a: The former first continues the operation, then itself + +, the latter is the first self + +, and then continue the operation;
  • The difference between a--and--a: ibid;
  • Cases:

    var m=10;
    var a=2;
    var m1=m+a++;
    var m2=m+++a;
    Console.log (M1);//11
    Console.log (m2);//13

Data type, operator