0317-JS variable data type operator control statement

key Memory ( routines ):
1. Key words: (must start with a letter, underscore (_), or dollar sign ($), identifier , variable (is a name, preferably preceded by a letter, is case-sensitive), constant (is a value with a data type)

　　Variable:

① Define and assign values

② use
2. Data type: numeric string boolean null undefined object

　　 data type conversions:　　 Alert (typeof information); //Determine the data type of the information

Other type-to-string: Global method String () //string (123)

　　　　　　　　　　　　　Number, Boolean available tostring () //(ture). ToString

　　　　String to number:parsefloat//Recommended Use

parseint (AA)//will take the whole

　　　　　　　　　　　Number (AA)//decimal operation will be problematic

3. Operators:

arithmetic operators:+-*/+ + (self-increase)-(self-subtract)% remainder

Self-increment and self-subtraction:

Only when you have a relationship with yourself, in front of no difference;

When participating in an expression: before //increment and re-operation in the back //first operation and then self-increment

assignment Operator:= + = = *=/=

+ =: A + = 2 ==> a = a+2;

relational operators:< > <= >=! = = = = = = = =

= =: Comparison value

= = = Comparison Value and type

Logical operators:

&&(with): Both sides are true, the result is true;

　　　　|| (OR) : as long as one side is true, the result is true;

! (non):! True=false;

　Ternary operators: //Handling simple (not true) judgments

An expression? Really do this: fake this;
4. Control statements

　　for--code Example:

    var dy= "";      for (var i=1;i<10;i++) {        for (var j=1;j<=i;j++) {                dy =dy+j+ "*" +i+ "=" +i*j+ "&nbsp;&nbsp;" ;        }                Dy=dy+ "<br/>";        }    document.getElementById ("Dayin"). Innerhtml=dy;

For loop print multiplication table

if--code example:

// title: 50 kg below 0.13 yuan per kilogram, exceeding the portion per kilogram of 0.2 yuan // Assign the weight of the baggage entered to W var w = prompt ("Enter your baggage weight (KG)"),    y; // calculate freight According to the weight entered if (w <=) {    = w * 0.13;} Else {    // Primitive: 50*1.3+ (w-50) *0.2;    y = w * 0.2-3.5;} // The output Freight alert ("You need to pay the shipping cost is" +y+ "Yuan");

Shipping Issues

　　switch--code Example:

Scissors Games: 0-Scissors 1-Fist 2-cloth//Assign the number you entered to youvaryou = prompt ("Please enter the 0/1/2 you want out of");//assign a computer's random number to a PCvarPC = parseint (Math.random () * 3);//alert ("Computer out of the number is" +pc);//judging the winning and losing according to the boxing situationSwitch(You) { Case"0":        Switch(PC) { Case0: Alert ("A very close");  Break;  Case1: Alert ("You lost.");  Break;  Case2: Alert ("You won.");  Break; default:             Break; }         Break;  Case"1":        Switch(PC) { Case0: Alert ("You won.");  Break;  Case1: Alert ("A very close");  Break;  Case2: Alert ("You lost.");  Break; default:             Break; }         Break;  Case"2":        Switch(PC) { Case0: Alert ("You lost.");  Break;  Case1: Alert ("You won.");  Break;  Case2: Alert ("A very close");  Break; default:             Break; }         Break; default:         Break;}

Scissors Mini Games

Array
Method (function)

A class is a set of commonalities.
An object is an XX in the collection and can have its attributes.

0317-JS variable data type operator control statement