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73 lines
1.9 KiB
JavaScript
73 lines
1.9 KiB
JavaScript
/**
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* @module ol/functions
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*/
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import { equals as arrayEquals } from './array.js';
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/**
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* Always returns true.
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* @return {boolean} true.
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*/
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export function TRUE() {
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return true;
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}
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/**
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* Always returns false.
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* @return {boolean} false.
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*/
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export function FALSE() {
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return false;
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}
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/**
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* A reusable function, used e.g. as a default for callbacks.
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*
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* @return {void} Nothing.
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*/
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export function VOID() { }
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/**
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* Wrap a function in another function that remembers the last return. If the
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* returned function is called twice in a row with the same arguments and the same
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* this object, it will return the value from the first call in the second call.
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*
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* @param {function(...any): ReturnType} fn The function to memoize.
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* @return {function(...any): ReturnType} The memoized function.
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* @template ReturnType
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*/
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export function memoizeOne(fn) {
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var called = false;
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/** @type {ReturnType} */
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var lastResult;
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/** @type {Array<any>} */
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var lastArgs;
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var lastThis;
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return function () {
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var nextArgs = Array.prototype.slice.call(arguments);
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if (!called || this !== lastThis || !arrayEquals(nextArgs, lastArgs)) {
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called = true;
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lastThis = this;
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lastArgs = nextArgs;
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lastResult = fn.apply(this, arguments);
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}
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return lastResult;
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};
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}
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/**
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* @template T
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* @param {function(): (T | Promise<T>)} getter A function that returns a value or a promise for a value.
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* @return {Promise<T>} A promise for the value.
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*/
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export function toPromise(getter) {
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function promiseGetter() {
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var value;
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try {
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value = getter();
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}
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catch (err) {
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return Promise.reject(err);
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}
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if (value instanceof Promise) {
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return value;
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}
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return Promise.resolve(value);
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}
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return promiseGetter();
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}
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//# sourceMappingURL=functions.js.map
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