HTML operators, type conversions

1.Type conversion:

is divided into automatic conversion and forced conversion, and forced conversion is generally used.

Convert other types to integers: parseInt();

Convert other types to decimals: parseFloat();

Determine whether it is a legal number type: isNaN();

is a number, it returns false, if it is not a number, it returns ture.

Example:

into the isNaN method

2.Operator:

Mathematical operators : + - * / % ++ --；

Relational operator : == ! = >= <= > <;

Logical operators : && || ! ;

Other operators : += -= *= /= %= ? : ;

3.Statement:

are generally divided into sequence, branch and loop statements.

(1) branch statement if:

(judgment condition)

Statements to be executed when conditions are met

Statement executed when the condition is not met

(2) loop for statement:

(initial condition; loop condition; state change)

Cycle

(3) Problem type: exhaustive, iterative.

(4) Two keywords: break and continue.

(5) If you want to output the value of a certain parameter: the output value is "+a+" and "+b"

<script></span></p> <p class="pre" align="justify">function visible1()</p> <p class="pre" align="justify">{ $("p").hide();};</p> <p class="pre" align="justify"></script>

Click here to make the text disappear"/>

<p>I will disappear.

$("id1") is equivalent to document.getElementById("id1")

Five practice questions

1. Input integers a and b. If a2+b2 is greater than 100, output a2+b2 with hundreds or more digits, otherwise output the sum of the two numbers






<script><br>function dianji()<br>{<br> var a = parseInt(document.getElementById("a").value);<br> var b = parseInt(document.getElementById("b ").value);<br> if(a*a+b*b>100)<br> {<br> alert(a*a+b*b);<br> }<br> else<br> {<br> alert(a+b); <br> } <br> }<br></script>

2. Enter a year to determine whether it is a leap year (a year that is evenly divisible by 4 but not 100. A century year that is evenly divisible by 400 is a leap year)


<script><br>function check()<br>{<br> var a =parseInt (document.getElementById("run").value);<br> if(a%4==0&&a%100!=0 || a%400==0)<br> {<br> alert("You entered a leap year") ;<br> }<br> else<br> {<br> alert("Not a leap year");<br> }<br>}<br></script>

3. Standard weight:
Men’s weight=height-100±3
Women’s weight=height-110±3


Please enter gender:

Please enter your height:

Please enter your weight:


<script><br>function tizhong()<br> {<br> var sex =document.getElementById("sex").value;<br> var height =parseFloat(document.getElementById("height").value);<br> var weight = parseFloat(document.getElementById("weight").value );<br> if(sex=="male")<br> {<br> var zhong = height-100-weight;<br> if(zhong<=3&&zhong>=-3)<br> {<br> alert("standard weight") <br> }<br> else if(zhong>3)<br> {<br> alert("Underweight, eat more") <br> }<br> else<br> {<br> alert("Overweight, exercise more") <br> }<br> }<br> else if(sex== "Female")<br> {<br> var zhong = height-110-weight;<br> if(zhong<=3&&zhong>=-3)<br> {<br> alert("standard weight") <br> }<br> else if(zhong>3)<br> { <br> alert("Underweight, eat more") <br> }<br> else<br> {<br> alert("Overweight, exercise more") <br> }<br> }<br> else<br> {<br> alert("Incorrect gender input!") <br> }<br>}<br></script>

4. For a game, the first 20 levels are each level’s own score.
Levels 21-30 are each 10 points.
Levels 31-40 are each 20 points.
Levels 41-49 are each level. 30 points
50 levels is 100 points
//Enter the number of levels you have passed now, and find the score you have now


Please enter the number of levels you have passed now:
<script><br>function jisuan()<br>{<br> var a = parseInt(document.getElementById("game").value);<br> if(a>0&&a<=50)<br> {<br> var sum=0;<br> for(var i=1;i<=a;i++)<br> {<br> if(i<=20)<br> {<br> sum+=i; <br> } <br> else if(i<=30)<br> {<br> sum+=10;<br> }<br> else if(i<=40)<br> {<br> sum+=20; <br> }<br> else if(i<=49)<br> {<br> sum+=30; <br> }<br> else<br> {<br> sum+=100; <br> }<br> }<br> alert("The total score you obtained is: "+sum)<br> } <br> else<br> {<br> alert("Incorrect input!") <br> } <br>}<br></script>

5. Enter the ages of 10 people from the console into the array, and sum the ages of the ten people

Please enter the first person in the text box Age: