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103 lines
2.2 KiB
JavaScript
103 lines
2.2 KiB
JavaScript
/**
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* Fisher-Yates shuffle.
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* http://stackoverflow.com/a/962890/373422
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* https://bost.ocks.org/mike/shuffle/
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* @param {Array} array Array to shuffle.
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* @return {Array} Randomly sorted array.
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*/
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function randomize(array) {
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let n = array.length;
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while (n) {
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n -= 1;
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const i = Math.floor(Math.random() * (n + 1));
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const temp = array[i];
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array[i] = array[n];
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array[n] = temp;
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}
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return array;
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}
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const defaults = {
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// Use array.reverse() to reverse the results
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reverse: false,
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// Sorting function
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by: null,
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// Custom sort function
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compare: null,
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// If true, this will skip the sorting and return a randomized order in the array
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randomize: false,
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// Determines which property of each item in the array is passed to the
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// sorting method.
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key: 'element',
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};
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/**
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* You can return `undefined` from the `by` function to revert to DOM order.
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* @param {Array<T>} arr Array to sort.
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* @param {SortOptions} options Sorting options.
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* @return {Array<T>}
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*/
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export default function sorter(arr, options) {
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// eslint-disable-next-line prefer-object-spread
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const opts = Object.assign({}, defaults, options);
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const original = Array.from(arr);
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let revert = false;
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if (!arr.length) {
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return [];
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}
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if (opts.randomize) {
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return randomize(arr);
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}
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// Sort the elements by the opts.by function.
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// If we don't have opts.by, default to DOM order
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if (typeof opts.by === 'function') {
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arr.sort((a, b) => {
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// Exit early if we already know we want to revert
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if (revert) {
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return 0;
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}
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const valA = opts.by(a[opts.key]);
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const valB = opts.by(b[opts.key]);
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// If both values are undefined, use the DOM order
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if (valA === undefined && valB === undefined) {
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revert = true;
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return 0;
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}
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if (valA < valB || valA === 'sortFirst' || valB === 'sortLast') {
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return -1;
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}
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if (valA > valB || valA === 'sortLast' || valB === 'sortFirst') {
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return 1;
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}
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return 0;
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});
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} else if (typeof opts.compare === 'function') {
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arr.sort(opts.compare);
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}
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// Revert to the original array if necessary
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if (revert) {
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return original;
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}
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if (opts.reverse) {
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arr.reverse();
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}
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return arr;
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}
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