javascript / expert
Snippet
Tagged Template Literal Generators for Middleware Intercept Control Flow
Using tagged template literals combined with generator functions allows creating declarative domain-specific evaluation rules for Next.js middleware execution and access control evaluation.
snippet.js
javascript
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export function* routeGuard(strings: TemplateStringsArray, ...values: boolean[]) {for (let i = 0; i < values.length; i++) {if (!values[i]) {yield `Blocked at rule segment: ${strings[i].trim()}`;return;}}yield `Allowed: ${strings.join('').trim()}`;}
nextjs
Breakdown
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export function* routeGuard(strings: TemplateStringsArray, ...values: boolean[]) {
Declares a generator tag function accepting literal template strings and rest boolean condition evaluations.
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for (let i = 0; i < values.length; i++) {
Iterates sequentially through supplied boolean condition results.
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if (!values[i]) {
Checks if current evaluation step failed authorization condition.
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yield `Blocked at rule segment: ${strings[i].trim()}`;
Yields early termination decision string pointing to exact failing template segment.
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return;
Terminates generator control flow immediately after failure.
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}
Closes if block.
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}
Closes evaluation loop.
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yield `Allowed: ${strings.join('').trim()}`;
Yields success evaluation state when all conditions pass.
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}
Closes generator function.