JS的初步语法

两种常见代码的引入方式；



如果js写在head中， 相当于是全局变量，

ctrl tab切换文件；
token就是令牌，你带着令牌接口才会承认。

let buf = "";

process.stdin.on("readable", function(){
    
    let chunk = process.stdin.read();
    if(chunk) buf+= chunk.toString()
;})

process.stdin.on("end", function(){
    
    // let [x,y] = buf.split(' ').map(x => {return parseInt(x)});
     let [x,y] = buf.split(' ').map(function(x){
    return parseInt(x)});
    let price = [4.00,4.50,5.00,2.00,1.50];
    let res = y * price[x - 1];
    console.log(`Total: R$ ${
      res.toFixed(2)}`);
    
})

注意看注释的哪一行， 二者都可以运行， 是等价的；

if else语句

let buf = "";
process.stdin.on("readable", function(){
    
    let chunk = process.stdin.read();
    if (chunk) buf += chunk.toString();
})

process.stdin.on("end", function(){
    
    // let a = buf.split('').map(x => {return x});
    //上面的这种方法是错误的；
    
    let a = parseFloat(buf);
    
    if(a >= 0 && a <= 25){
    
        console.log("Intervalo [0,25]");
    }
     else if (a>25 && a <= 50)
    {
    
        console.log("Intervalo (25,50]");
    }
    else if( a > 50 && a <= 75)
    {
    
        console.log("Intervalo (50,75]");
    }
    else if (a > 75 && a <= 100)
    {
    
        console.log("Intervalo (75,100]");
    }
    else
    {
    
        console.log("Fora de intervalo");
    }
})

let buf = "";

process.stdin.on("readable", function() {
    
    let chunk = process.stdin.read();
    if (chunk) buf += chunk.toString();
});

process.stdin.on("end", function() {
    
    let [a, b, c] = buf.split('\n');

    if (a === "vertebrado") {
    
        if (b === "ave") {
    
            if (c === "carnivoro") {
    
                console.log("aguia");
            } else {
    
                console.log("pomba");
            }
        } else {
    
            if (c === "onivoro") {
    
                console.log("homem");
            } else {
    
                console.log("vaca");
            }
        }
    } else {
    
        if (b === "inseto") {
    
            if (c === "hematofago") {
    
                console.log("pulga");
            } else {
    
                console.log("lagarta");
            }
        } else {
    
            if (c === "hematofago") {
    
                console.log("sanguessuga");
            } else {
    
                console.log("minhoca");
            }
        }
    }
});

上面的部分， 注意split()中的部分是根据’\n’;不是空格；

• 循环
  eg721递增序列:

let x;//记得有需要初始化

let buf = '';

process.stdin.on("readable", function(){
    
    let chunk = process.stdin.read();
    if (chunk) buf += chunk.toString();
});

process.stdin.on("end", function(){
    
    let xs = buf.split('\n').map(function(x){
    
        return parseInt(x);
    });

    for (let x of xs){
    
        if (x === 0) break;
        let line = "";
        for (let i = 1; i <= x; i ++)
            line += `${
      i} `; //因为console.log()存在回车 故我们先拼接字符串然后再回车
        console.log(line); 
    }
});

因为console.log()存在回车 故我们先拼接字符串然后再回车

    let n = parseInt(buf);
    // let m = n/2;
    let m = parseInt(n / 2);

注意m这里是不一样的,必须通过

 let m = parseInt(n / 2);

这种， 而不能直接等于n/2;

• 数组
  

process.stdin.on("end", function(){
    
    let lines  = buf.split('\n');
    
    let n = parseInt(lines[0]);
    let op = lines[1];
    
    let d = [];
    for(let i = 0 ; i < 12 ; i ++)
    {
    
        d.push(lines[i+2].split(' ').map(x => {
    return parseFloat(x)}))
    }
    
    let sum = 0;
    for(let i = 0 ; i <12 ; i ++ )
        sum+=d[n][i];
        
    if(op==='M') sum/=12;
    
    console.log(`${
      sum.toFixed(1)}`);
       
})

好好体会分块的思想吧；

• 函数

let buf = "";

process.stdin.on("readable", function() {
    
    let chunk = process.stdin.read();
    if (chunk) buf += chunk.toString();
});

let max = (x, y) => {
    
    return x > y ? x : y;
};

process.stdin.on("end", function() {
    
    let [x, y] = buf.split(' ').map(x => {
    return parseInt(x)});
    console.log(max(x, y));
});