我有一个这样的数组:

var arr1 = ["a", "b", "c", "d"];

我如何随机化/打乱它?


当前回答

使用Ramda的功能解决方案。

const {map, compose, sortBy, prop} = require('ramda')

const shuffle = compose(
  map(prop('v')),
  sortBy(prop('i')),
  map(v => ({v, i: Math.random()}))
)

shuffle([1,2,3,4,5,6,7])

其他回答

// Create a places array which holds the index for each item in the
// passed in array.
// 
// Then return a new array by randomly selecting items from the
// passed in array by referencing the places array item. Removing that
// places item each time though.
function shuffle(array) {
    let places = array.map((item, index) => index);
    return array.map((item, index, array) => {
      const random_index = Math.floor(Math.random() * places.length);
      const places_value = places[random_index];
      places.splice(random_index, 1);
      return array[places_value];
    })
}

重建整个阵列,逐个将每个元素放在一个随机位置。

[1,2,3].reduce((a,x,i)=>{a.splice(Math.floor(Math.random()*(i+1)),0,x);return a},[])

变量ia=[1,2,3];var it=1000;var f=(a,x,i)=>{a.splice(Math.floor(Math.random()*(i+1)),0,x);返回a};var a=新数组(it).fill(ia).map(x=>x.reduce(f,[]));var r=新数组(ia.length).fill(0).map((x,i)=>a.reduce((i2,x2)=>x2[i]+i2,0)/it)console.log(“这些值应该相当相等:”,r);

使用排序方法和数学方法:

var arr =  ["HORSE", "TIGER", "DOG", "CAT"];
function shuffleArray(arr){
  return arr.sort( () => Math.floor(Math.random() * Math.floor(3)) - 1)  
}

// every time it gives random sequence
shuffleArr(arr);
// ["DOG", "CAT", "TIGER", "HORSE"]
// ["HORSE", "TIGER", "CAT", "DOG"]
// ["TIGER", "HORSE", "CAT", "DOG"]
//one line solution
shuffle = (array) => array.sort(() => Math.random() - 0.5);


//Demo
let arr = [1, 2, 3];
shuffle(arr);
alert(arr);

https://javascript.info/task/shuffle

Math.random()-0.5是一个随机数,可以是正数或负,所以排序函数会随机地重新排序元素。

使用Fisher Yates shuffle算法和ES6:

// Original array
let array = ['a', 'b', 'c', 'd'];

// Create a copy of the original array to be randomized
let shuffle = [...array];

// Defining function returning random value from i to N
const getRandomValue = (i, N) => Math.floor(Math.random() * (N - i) + i);

// Shuffle a pair of two elements at random position j
shuffle.forEach( (elem, i, arr, j = getRandomValue(i, arr.length)) => [arr[i], arr[j]] = [arr[j], arr[i]] );

console.log(shuffle);
// ['d', 'a', 'b', 'c']