12月16日JS基础(变量.流程控制.循环.类型转换)-九期线上班 - 作业

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javascript变量、函数的定义

<script type="text/javascript">
//变量声明
var a=666;
//输出变量
console.log(a);
//函数定义
function fun(){
console.log('666666666');
}
//函数调用
fun();
</script>

javascript流程控制if else switch

<script type="text/javascript">
//流程控制 IF
function a1(){
    var int=1;
    if (int>100 || int<0) {
        alert('非约定值！！！');
    }else if (int>90) {
        alert('优秀！');
    }else if (int<=90 && int>70) {
        alert('及格了');
    }else{
        alert('没及格 快跑！');
    }
}
//流程控制 switch
function a2() {
    var int=99;
    switch(true){
        case(int >100 || int < 0):
        alert('分错了！');
        break;
        case(int>=90):
        alert('优秀了！');
        break;
        case(int>=70):
        alert('及格了！');
        break;
        default:
        alert('挨打了！');
    }
}
//流程控制 IF优化
function a3(){
    var int=1000;
    if (int >100 || int < 0) {
        alert('报错');
    }
    if (int>=90 && int <= 100 && int >=0) {
        alert('优秀');
    }
    if (int<=90 && int>=70) {
        alert('及格');
    }
    if (int<70) {
        alert('没过')
    }
}
a3();
</script>

javascript三种循环

<script type="text/javascript">
//循环 for
function x1(){
    for (var i = 1; i <=10; i++) {
        console.log(i);
    }
}
//循环 while
function x2() {
    var i=10;
    while(i<=100){
        console.log(i);
        i+=10;
    }
}
//循环 do while
function x3() {
    var i=2;
    do{
        console.log(i);
        i+=2;
    }while (i<=20);
}
x3();
</script>

数据类型转换：parseInt、isNaN函数的使用

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>数据类型转换：parseInt、isNaN函数的使用</title>
</head>
<body>
    <h1>数据类型转换：parseInt、isNaN函数的使用</h1>
    <input type="text" name="" id="age" placeholder="输入您的年龄">
    <button onclick="ageJc();">提交</button>
    <script type="text/javascript">
    function ageJc() {
        var age=document.getElementById('age').value;
        age = parseInt(age);
        //isNaN判断值是否为NaN
        if (isNaN(age)) {
            return alert('年龄值不合法！');
        }
        if (age>120 || age<0) {
            return alert('年龄超过可提交范围，请核实');
        }
        return alert('您的年龄为【'+age+'】已提交成功！')
    }
    </script>
</body>
</html>

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