* JavaScript referred to as JS
* JavaScript What is that?
* Is a scripting language: does not need to compile, run directly
* Is an interpreted language: encountered the same code is interpreted line of code
* C # language is an object-oriented language, is also a compiled language, is used .net technology
* Is a dynamically typed language --- not resolved
* Is an object-based language --- not explain
* Is a weakly typed language, variables when they are declared using the var
（
）
* Strongly typed languages: C # is ----->
* Stores a number: int num = 10; float num2 = 90.3;
* JS divided into three parts:
* 1. ECMAScript standard: basic syntax of js
* 2. JUDGMENT
* 3. GOOD
* JS nearly 10 days with the invention
* --- variable effect: operational data (stored data, the read data)
* Variable declaration:
* Var variable name;
* There num;
* Initialize variables
* Var variable name = value; ----> literal way of assignment
* Var str = "You Well";
* Js the case is distinguishable
* String js can use single quotes, double quotes can also be used temporarily recommend the use of double quotes ---
* Js the end of each line of code to have a semicolon;
* type of data:
* Js the primitive data types: number, string, boolean, undefined, null, object
* Null and undefined data is not much sense, null is the location of the object makes sense to speak ---
* NaN ---- not a number, not a number and a digital calculation ---> The result is NaN
* IsNaN () ---> determines the value of this variable is not or not a number is not a number --- if the result is true, false if the result is a number
*
* Number of data types ---- either integer or fractional number data types are
---- * string data type string, get the length of the string: variable name .length
--- * boolean data type two values, true, false
* Null ---- only one, null
* Undefined ---- only one, undefined, a variable declaration, and no assignment
* Object --- ----- Object Object Oriented time to explain
*
* Type conversion:
* Other types of digital revolution
* ParseInt () ----> to Integer
* ParseFloat () ---> turn decimals
Two strict * Number () ----> digital revolution than the above -----
* Other types to String
* .toString()
* String();
*
* Other types of transfer boolean
* Boolean () ----> is either true or false
*
* Operator: operator ----
* Arithmetic operators: + - * /%
* Composite Operators: + = - = = * / =% =
* Assignment operator: = lowest priority
* Unary operators: + -
* Ternary operator:?:
* Relational operators:> <> = <= = == === ==!!
* Logical operators: && ||!
*
* Results relational operators are Boolean
* Results logical operators are Boolean type
*
* Expression 1 && expression 2
* If there is a false, the entire result is false
* 2 expression expression 1 ||
* Only a true, the overall result is true
*! Expression --- the result is negated
*
* Exercise: swap the values of two variables
1. The first variable exchange ideas: the use of third-party exchange temp
// first variable exchange ideas: the use of third-party exchange temp
var num1 = 10;
var = 20 is num2;
value // num1 first taken out in the temp
temp = num1;
// then the value num2 num1 taken out on the
num1 num2 =;
// finally taken out on the value of temp num2
num2 = temp;
the console.log (num1, num2); 10 // 20 is
2. The second way exchange: generally applicable to digital
The second exchange of //: generally applicable to digital
var num1 = 10;
var = 20 is num2;
// the value num1 num2 variable values and variables, adding taken out, re-assigned to num1
num1 = num1 + num2; // 30
// the variables values num1 and num2 variables taken out, the result of subtraction to reassign num2
num2 = num1 - num2; 30-20 = 10 //
// the value num1 and num2 variables the value of the variable is taken out, the result of subtraction to reassign num1
num1 = num1 - num2; // 30-10 = 20 is
the console.log (num1, num2) // 20 is 10
3. Third: expansion, variable exchange, Bitwise
// Third: expansion, variable exchange, Bitwise
var num1 = 10;
var = 20 is num2;
num1 num2 ^ = num1;
num2 = ^ num1 num2;
num1 = num1 num2 ^;
the console.log (num1, num2); // 2010