while循环应用（各种小练习）

练习1：1+…+100等于

let i = 1,num=0;
while(i<=100){
    num+=i;    
    i++;    
}
console.log(num);

练习2：100以内奇数项的和与偶数项的和

let odd=0,even=0,i=1;
while(i<=100){
    //法1：
    if(i%2==0){
        even+=i;
    }else{
        odd+=i;        
    }
    i++;

    //法2：
    //i%2==0?odd+=i:even+=i;
    //i++;
}
console.log("奇数是："+odd+",偶数是："+even);

练习3：水仙花数

const readline = require('readline-sync');
let i = true;
while (i) {
    console.log('请用户输入一个三位数,输入0退出');
    let sum = readline.question();
    if(sum==0){
        break;
    }
    if (sum.length == 3) {
        sum -= 0;
        let gw, sw, bw;
        gw = sum % 10;
        sw = parseInt(sum % 100 / 10);
        bw = parseInt(sum / 100);
        if (sum == (gw ** 3 + sw ** 3 + bw ** 3)) {
            console.log(`${sum}是水仙花数`);
        } else {
            console.log(`${sum}不是水仙花数`);
        }
        // console.log(gw,sw,bw);
    } else {
        console.log('非法输入');
    }
}

练习4：判断回文12321

const readline = require('readline-sync');
let i = true;
while (i) {
    console.log('请用户输入一个数,输入0退出');
    let sum = readline.question();
    if (sum == 0) {
        break;
    }
    // let gw, sw, bw;
    gw = sum % 10;
    sw = parseInt(sum % 100 / 10);
    bw = parseInt(sum % 1000 / 100);
    qw = parseInt(sum % 10000 / 1000)
    ww = parseInt(sum / 10000)
    len = sum.length;
    // console.log(gw, sw, bw, qw, ww);
    if (gw==ww&&sw==qw) {
        console.log(`${sum}是回文数`);
    } else {
        console.log(`${sum}不是回文数`);
    }

}

练习5：判断回文，while和for循环嵌套

const readline = require('readline-sync');
let i = true;
while (i) {
    console.log('请用户输入一个数,输入0退出');
    let sum = readline.question();
    if (sum == 0) {
        break;
    }
    str = sum.length;
    let s = true;    
    for(let j=0,o=str-1;j<=parseInt(str/2);j++,o--){
        if(sum[j]!=sum[o]) {
            s=false;
        }        
    }
    if(s==true){
        console.log('是回文');
    }else{
        console.log('不会回文');
    }

}