1234567891011121314151617181920212223242526272829303132333435363738394041424344454647484950515253
/** * A [Fisher-Yates shuffle](http://en.wikipedia.org/wiki/Fisher%E2%80%93Yates_shuffle) * in-place - which means that it **will change the order of the original * array by reference**. * * This is an algorithm that generates a random [permutation](https://en.wikipedia.org/wiki/Permutation) * of a set. * * @param {Array} x sample of one or more numbers * @param {Function} [randomSource=Math.random] an optional entropy source that * returns numbers between 0 inclusive and 1 exclusive: the range [0, 1) * @returns {Array} x * @example * var x = [1, 2, 3, 4]; * shuffleInPlace(x); * // x is shuffled to a value like [2, 1, 4, 3] */function shuffleInPlace(x, randomSource) {    // a custom random number source can be provided if you want to use    // a fixed seed or another random number generator, like    // [random-js](https://www.npmjs.org/package/random-js)    randomSource = randomSource || Math.random;
    // store the current length of the x to determine    // when no elements remain to shuffle.    let length = x.length;
    // temporary is used to hold an item when it is being    // swapped between indices.    let temporary;
    // The index to swap at each stage.    let index;
    // While there are still items to shuffle    while (length > 0) {        // choose a random index within the subset of the array        // that is not yet shuffled        index = Math.floor(randomSource() * length--);
        // store the value that we'll move temporarily        temporary = x[length];
        // swap the value at `x[length]` with `x[index]`        x[length] = x[index];        x[index] = temporary;    }
    return x;}
export default shuffleInPlace;