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How to shuffle an array in JavaScript
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Shuffle an array
Let’s write a shuffle function to randomly reorder elements of the array. For this, we will:
- Loop through all elements of the array one by one
- Generate a random index with
Math.random() will return a random floating-point number between 0and1 - Swap the
currentIndexelement with generatedrandom index.
Function to shuffle array
function shuffleArray(array) {
let len = array.length,
currentIndex;
for (currentIndex = len - 1; currentIndex > 0; currentIndex--) {
let randIndex = Math.floor(Math.random() * (currentIndex + 1) );
var temp = array[currentIndex];
array[currentIndex] = array[randIndex];
array[randIndex] = temp;
}
}
let a = [1,2,3,4,5];
console.log("Array before Shuffling", a);
console.log("Shuffling array");
shuffleArray(a);
console.log("Array after Shuffling", a);In the code above we generate a random index using Math.random() * (curentIndex + 1). This will give a random index between 0(included) and currentIndex+1(excluded). In our case, if the currentIndex = 4, upon executing Math.random() * (curentIndex + 1), we will get a random number between 0(included) - 5(excluded) (i.e., any one from this number 0,1,2,3,4).
The code above will shuffle the elements in the original array. If you don’t want to shuffle the original array, make a clone of the original array and pass the cloned array to the shuffle function.
You can clone an array using
array.slice(0).
function shuffleArray(array) {
let len = array.length,
currentIndex;
for (currentIndex = len - 1; currentIndex > 0; currentIndex--) {
let randIndex = Math.floor(Math.random() * (currentIndex + 1) );
var temp = array[currentIndex];
array[currentIndex] = array[randIndex];
array[randIndex] = temp;
}
}
let a = [1,2,3,4,5];
// clone using slice method
let clonedArray = a.slice(0);
console.log("cloned array before shufflling " ,clonedArray);
shuffleArray(clonedArray);
console.log("cloned array after shufflling " ,clonedArray);
console.log("source array after shuffling" ,a); RELATED TAGS
javascript
array
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