An educational pure functional programming library in TypeScript
Refactor branded-types.md examples to expression style
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docs/guides/concepts/branded-types.md
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docs/guides/concepts/branded-types.md
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type OrderId = Branded<string, "OrderId">
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const OrderId = (value: string): Option<OrderId> => {
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if (!value.startsWith("order-")) {
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return none
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}
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return some(value as OrderId)
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}
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const OrderId = (value: string): Option<OrderId> =>
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value.startsWith("order-") ? some(value as OrderId) : none
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```
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Now invalid IDs are caught at creation:
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const Email = (s: string): Option<Email> =>
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/^[^\s@]+@[^\s@]+\.[^\s@]+$/.test(s) ? some(s as Email) : none
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// Note: try/catch is an allowed exception to the "no early returns" rule
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// because it bridges impure JavaScript APIs
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const Url = (s: string): Option<Url> => {
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try {
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new URL(s)
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return some(s as Url)
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return (new URL(s), some(s as Url))
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} catch {
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return none
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}