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75 lines
2.9 KiB
TypeScript
75 lines
2.9 KiB
TypeScript
// Array construction, iteration, holes, and mapper mutations.
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const numeric = new Array<number>(4);
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console.log("count", numeric.length, 0 in numeric, numeric[0] === undefined);
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numeric[1] = 12;
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console.log("count-write", numeric.length, 1 in numeric, 2 in numeric, numeric[1]);
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const words = new Array<string>(2);
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console.log("word-holes", words.length, 0 in words, words[0] === undefined);
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console.log("elements", new Array(5, 6).join("|"), new Array("5").join("|"));
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const called: number[] = Array(3);
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console.log("called", called.length, 0 in called);
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console.log("called-elements", Array(5, 6).join("|"), Array("5").join("|"));
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function mixedArgument(value: number | string): void {
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const made = new Array<number | string>(value);
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console.log("mixed", made.length, 0 in made, made[0]);
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}
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mixedArgument(3);
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mixedArgument("three");
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try {
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mixedArgument(-1);
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} catch (error) {
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if (error instanceof Error) console.log("mixed-invalid", error.name, error.message);
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}
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console.log("of", Array.of(5).join("|"), Array.of(1, 2, 3).join("|"), Array.of<string>().length);
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const spread = [8, 9];
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console.log("of-spread", Array.of(7, ...spread, 10).join("|"));
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const sparseSpread: number[] = [];
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sparseSpread.length = 2;
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sparseSpread[1] = 4;
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const spreadWithHole = Array.of(...sparseSpread);
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console.log("of-hole", spreadWithHole.length, 0 in spreadWithHole, spreadWithHole[0] === undefined, spreadWithHole[1]);
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function invalidLength(length: number): void {
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try {
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new Array<number>(length);
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} catch (error) {
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if (error instanceof Error) console.log("invalid", length, error.name, error.message);
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}
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}
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invalidLength(-1);
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invalidLength(2.5);
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invalidLength(4294967296);
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const sparse: number[] = [];
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sparse.length = 3;
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sparse[1] = 7;
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const copy = Array.from(sparse);
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console.log("copy", copy.length, 0 in copy, 1 in copy, 2 in copy, copy[0] === undefined, copy[1]);
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console.log("source", 0 in sparse, 1 in sparse, 2 in sparse);
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const mapped = Array.from(sparse, (value, index) => `${index}:${value === undefined ? "missing" : value}`);
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console.log("mapped", mapped.join("|"));
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const records = [{ id: 1 }, { id: 2 }];
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const shallow = Array.from(records);
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console.log("identity", shallow !== records, shallow[0] === records[0], shallow[1] === records[1]);
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const singleton = Array.of(records[0]!);
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console.log("of-reference", singleton[0] === records[0]);
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console.log("set", Array.from(new Set([3, 1, 3, 2])).join("|"));
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console.log("string-map", Array.from("A💫B", (character, index) => `${index}:${character}`).join("|"));
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const growing = [2, 3];
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const grown = Array.from(growing, (value, index) => {
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if (index === 0) growing.push(4);
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return value * 10 + index;
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});
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console.log("grow", grown.join("|"), growing.length);
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const shrinking = [2, 3, 4];
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const shrunk = Array.from(shrinking, (value, index) => {
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if (index === 0) shrinking.length = 1;
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return value;
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});
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console.log("shrink", shrunk.join("|"), shrinking.length);
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