59 lines
1.4 KiB
Markdown
59 lines
1.4 KiB
Markdown
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---
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tags:
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- typescript
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---
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# Function overloads
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Function overloading is not a feature of JavaScript but something close to it
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can be achieved with TypeScript. It proceeds by defining multiple function types
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(defined above the function) that may serve as the actual function's parameters.
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Then with the actual function, you leave the changeable parameters open as
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optional unions and/or `unknown` :
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```ts
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// First oveload type:
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function logSearch(term: string, options?: string): void;
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// Second overload type:
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function logSearch(term: string, options?: number): void;
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// Implementation:
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function logSearch(term: string, p2?: unknown) {
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let query = `https://searchdatabase/${term}`;
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if (typeof p2 === "string") {
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query = `${query}/tag=${p2}`;
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console.log(query);
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} else {
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query = `${query}/page=${p2}`;
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console.log(query);
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}
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}
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logSearch("apples", "braeburn");
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logSearch("bananas", 3);
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```
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```ts
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// First overload type:
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function logSearchUnion(term: string, options?: string): void;
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// Second overload type:
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function logSearchUnion(term: string, options?: number): void;
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// Implementation:
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function logSearchUnion(term: string, p2?: string | number) {
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let query = `https://searchdatabase/${term}`;
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if (typeof p2 === "string") {
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query = `${query}/tag=${p2}`;
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console.log(query);
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} else {
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query = `${query}/page=${p2}`;
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console.log(query);
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}
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}
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logSearchUnion("melon", "honey-dew");
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logSearchUnion("oranges", 4);
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```
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