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82 lines
2.6 KiB
82 lines
2.6 KiB
5 months ago
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// A [trie](https://en.wikipedia.org/wiki/Trie) data structure that holds
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// object keys weakly, yet can also hold non-object keys, unlike the
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// native `WeakMap`.
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// If no makeData function is supplied, the looked-up data will be an empty,
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// null-prototype Object.
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const defaultMakeData = () => Object.create(null);
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// Useful for processing arguments objects as well as arrays.
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const { forEach, slice } = Array.prototype;
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const { hasOwnProperty } = Object.prototype;
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export class Trie {
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constructor(weakness = true, makeData = defaultMakeData) {
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this.weakness = weakness;
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this.makeData = makeData;
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}
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lookup() {
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return this.lookupArray(arguments);
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}
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lookupArray(array) {
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let node = this;
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forEach.call(array, key => node = node.getChildTrie(key));
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return hasOwnProperty.call(node, "data")
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? node.data
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: node.data = this.makeData(slice.call(array));
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}
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peek() {
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return this.peekArray(arguments);
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}
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peekArray(array) {
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let node = this;
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for (let i = 0, len = array.length; node && i < len; ++i) {
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const map = node.mapFor(array[i], false);
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node = map && map.get(array[i]);
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}
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return node && node.data;
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}
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remove() {
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return this.removeArray(arguments);
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}
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removeArray(array) {
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let data;
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if (array.length) {
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const head = array[0];
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const map = this.mapFor(head, false);
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const child = map && map.get(head);
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if (child) {
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data = child.removeArray(slice.call(array, 1));
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if (!child.data && !child.weak && !(child.strong && child.strong.size)) {
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map.delete(head);
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}
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}
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}
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else {
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data = this.data;
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delete this.data;
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}
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return data;
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}
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getChildTrie(key) {
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const map = this.mapFor(key, true);
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let child = map.get(key);
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if (!child)
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map.set(key, child = new Trie(this.weakness, this.makeData));
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return child;
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}
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mapFor(key, create) {
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return this.weakness && isObjRef(key)
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? this.weak || (create ? this.weak = new WeakMap : void 0)
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: this.strong || (create ? this.strong = new Map : void 0);
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}
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}
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function isObjRef(value) {
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switch (typeof value) {
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case "object":
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if (value === null)
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break;
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// Fall through to return true...
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case "function":
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return true;
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}
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return false;
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}
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//# sourceMappingURL=index.js.map
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