explain problem: When you click the button, the background color changes randomly. I am trying to count the number of cases where the color blue appears.
summarize the problem: The number of color arrays and the number of blues are not output. I don’t know how to implement 4C2 in JavaScript
Describe tried: I tried to check the number of arrays in console.log in advance Analyze the code of https://craftjj.neocities.org/index.1.html I’ve been trying to find a way to implement combinations in javascript.
const body = document.querySelector('body') const btn = document.querySelector('.btn') const cBtn = document.querySelector('.cbtn') const color = ['red','blue','pink','blue','yellow'] function conbination(){ const colorNum = color.length//color배열 개수[color array count] const blueNum = color['blue'].length//blue개수[blue count] console.log(colorNum) console.log(blueNum) } /*const n = 4 const r = 2 function c(n, r) { return Math.floor(p(n, r) / times(1,r)); } */ btn.addEventListener("click",()=>{ let n = Math.floor(Math.random() * 5); body.style.backgroundColor = color[n] }) function init(){ cBtn.addEventListener('click',conbination) }
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Answer
const combination=function(n,k){ let nfact=1,kfact=1; for(let i=n;i>n-k;i--){ nfact*=i; } for(let i=k;i>0;i--){ kfact*=i; } return Math.floor(nfact/kfact); }
This will give you the roundoff value of combination for C(n,k)…