将数组的随机正值转换为负数

Question

I'm a JS newcomer. I have a scrambled array of numbers and need to convert random positive values of the array into negative. At that point I only know how to randomize the array:

var myArray = [1,2,3,4,5,6,7,8,9,10];
myArray.sort(function() {
    return 0.5 - Math.random()
}) 

But need the result look something like this: [8,-2,3,9,-5,-1,4,7,6,-10]

Please suggest. Thank you!

Answer 1

myArray.forEach(function(i,j){

if(i>0){

  var negative=i*(-1);/*convert your positive values to negative*/
  myArray[j]=negative;

}

})

Answer 2

Modified Fisher–Yates shuffle to randomly negate the item

function shuffle2(arr) {
    var i, j, e;
    for (i = 0; i < arr.length; ++i) { // for every index
        j = Math.floor(Math.random() * (arr.length - i)); // choose random index to right
        e = arr[i]; // swap with current index
        arr[i] = arr[i + j];
        arr[i + j] = e;
        if (.5 > Math.random()) // then, randomly
            arr[i] = -arr[i]; // flip to negative
    }
    return arr;
}

Now can do

shuffle2(myArray); // [-5, 2, 6, -7, -10, 1, 3, -4, -9, -8]

---

Please note if you were to stop the loop at arr.length - 1 you will need a final random flip outside of the loop for the last index

Answer 3

You can transform your array using Array.prototype.map() to get random +/- like this:

myArray = myArray.map(function(item) {
    return Math.random() > 0.5 ? item : -item; // random +/-
});

Map function does not modify your array but only returns new mapped one (so you have to reassign it or assign to a new variable).

Answer 4

How about adding a second random number for positiv / negative (Flipping coin):

var pos = Math.floor(Math.random()*10) % 2;
var num = Math.random() * 10;
var result;
// pos will evaluate false if it is 0
// or true if it is 1
result = pos ? num : -num;

return result;

Answer 5

As you are a new comer this is the easiest way. Used for loop and Math.floor()

1. First randomize the array.
2. Use math.random()*myArray.length and for loop to generate a random number and change the value of the index corresponding to the number value eg-

for (i = 0; i < 10; i++){
  var arrVal = myArray[Math.floor( Math.random()*myArray.length);]
if(arrVal > 0){
  arrVal = arrVal*(-1);
};
  };