47 lines
1.2 KiB
TypeScript
47 lines
1.2 KiB
TypeScript
import { identity } from "./composition.ts";
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type cmpArgs = Readonly<{ key: (item: any) => any; reverse: boolean }>;
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const cmpDefaults: cmpArgs = { key: identity, reverse: false };
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/**
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* Compare operator, that can be used in sort() calls.
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*/
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export function cmp(args?: Partial<cmpArgs>): (a: any, b: any) => number {
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const fargs = { ...cmpDefaults, ...args };
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return (a, b) => {
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const ka = fargs.key(a);
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const kb = fargs.key(b);
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if (ka > kb) {
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return fargs.reverse ? -1 : 1;
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} else if (ka < kb) {
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return fargs.reverse ? 1 : -1;
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} else {
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return 0;
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}
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};
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}
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/**
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* Get a function to check the strict equality with a reference
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*/
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export function is<T, S extends T>(
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ref: T,
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): (input: S) => input is Extract<T, S> {
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return (x): x is Extract<T, S> => x === ref;
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}
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/**
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* Convert a value to a boolean (are considered falsy: 0, false, "", {}, [], null, undefined)
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*/
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export function bool<T>(value: T | null | undefined): value is T;
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export function bool(value: any): boolean {
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if (!value) {
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return false;
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} else if (value instanceof Set) {
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return value.size > 0;
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} else if (typeof value == "object") {
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return Object.keys(value).length > 0;
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} else {
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return true;
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}
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}
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