请问 js 如何统计个数 - V2EX
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aglsv

请问 js 如何统计个数

  •  
  •   aglsv Jul 27, 2020 3251 views
    This topic created in 2102 days ago, the information mentioned may be changed or developed.

    让求 1~500 内所有不包含 4 的自然数的个数,我现在只会输出这些自然数,不知道如何统计,求教啊

    <script> var a,b,c for(i=1;i<=500;i++){ a = parseInt(i/100) b = parseInt((i-a*100)/10) c = parseInt(i-a*100-b*10) if(a!==4 && b!== 4 && c!== 4){ document.write(i+'<br>') } } </script> 
    summerwar
        1
    summerwar  
       Jul 27, 2020
    弄个数组放进去
    9yu
        2
    9yu  
       Jul 27, 2020 via Android   1
    让后端写个接口给你返回 /:doge
    yuenc
        3
    yuenc  
       Jul 27, 2020
    ```js
    <script>
    let 个数 = 0;
    for(i=1;i<=500;i++) {
    if(!`${i}`.includes(4)) {
    个数++
    }
    }
    document.write(个数)
    <script>
    ```
    aglsv
        4
    aglsv  
    OP
       Jul 27, 2020
    @summerwar 请问这个该咋弄
    aglsv
        5
    aglsv  
    OP
       Jul 27, 2020
    @yuenc 谢谢老哥了 TvT 可算是做出来了
    aglsv
        6
    aglsv  
    OP
       Jul 27, 2020
    @9yu 我的后端同学找对象去了……
    9yu
        7
    9yu  
       Jul 27, 2020 via Android
    @aglsv “我的后端同学”,想听职场上的爱情故事
    只要成为后端得对象,这个问题就完美解决了
    autoxbc
        8
    autoxbc  
       Jul 27, 2020
    这是个排列组合题,有解析解
    yggd
        9
    yggd  
       Jul 27, 2020
    let list = document.getElementByTagName('br');
    document.write(list.length);
    azh7138m
        10
    azh7138m  
       Jul 27, 2020
    可这,就是个普通的编程题,和语言的关系也不大。。。。
    aglsv
        11
    aglsv  
    OP
       Jul 27, 2020 via Android
    @azh7138m 刚学了一天,原来就写过 c 语言,还是几年前的事
    donghui1993
        12
    donghui1993  
       Jul 28, 2020
    new Array(500).fill(0).map((_,i)=>i+1).filter((num)=>!/4{1,}/.test(num)).length
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