{"id":9465,"date":"2025-04-22T15:32:23","date_gmt":"2025-04-22T14:32:23","guid":{"rendered":"https:\/\/solidt.eu\/site\/?p=9465"},"modified":"2026-01-05T17:00:05","modified_gmt":"2026-01-05T16:00:05","slug":"typescript-generic-iteratorwrapper","status":"publish","type":"post","link":"https:\/\/solidt.eu\/site\/typescript-generic-iteratorwrapper\/","title":{"rendered":"Typescript Generic IteratorWrapper"},"content":{"rendered":"\n<div style=\"height: 250px; position:relative; margin-bottom: 50px;\" class=\"wp-block-simple-code-block-ace\"><pre class=\"wp-block-simple-code-block-ace\" style=\"position:absolute;top:0;right:0;bottom:0;left:0\" data-mode=\"typescript\" data-theme=\"monokai\" data-fontsize=\"14\" data-lines=\"Infinity\" data-showlines=\"true\" data-copy=\"false\">function from&lt;T>(iterable: Iterable&lt;T>): IteratorWrapper&lt;T> {\n    return new IteratorWrapper(iterable);\n}\n\nfunction* map&lt;T, U>(iter: Iterator&lt;T>, f: (value: T) => U): Generator&lt;U> {\n    for (let x of iterableFromIterator(iter)) {\n        yield f(x);\n    }\n}\n\nfunction* filter&lt;T>(iter: Iterator&lt;T>, f: (value: T) => boolean): Generator&lt;T> {\n    for (let x of iterableFromIterator(iter)) {\n        if (f(x)) yield x;\n    }\n}\n\nfunction* take&lt;T>(iter: Iterator&lt;T>, n: number): Generator&lt;T> {\n    let i = 0;\n    for (let x of iterableFromIterator(iter)) {\n        if (i++ &lt; n) yield x;\n        else break;\n    }\n}\n\nfunction* skip&lt;T>(iter: Iterator&lt;T>, n: number): Generator&lt;T> {\n    let i = 0;\n    for (let x of iterableFromIterator(iter)) {\n        if (i++ >= n) yield x;\n    }\n}\n\nfunction iterableFromIterator&lt;T>(iter: Iterator&lt;T>): Iterable&lt;T> {\n    return {\n        [Symbol.iterator]() {\n            return iter;\n        }\n    };\n}\n\nclass IteratorWrapper&lt;T> implements Iterable&lt;T> {\n    private iter: Iterator&lt;T>;\n\n    constructor(iterable: Iterable&lt;T>) {\n        this.iter = iterable[Symbol.iterator]();\n    }\n\n    [Symbol.iterator](): Iterator&lt;T> {\n        return this.iter;\n    }\n\n    map&lt;U>(f: (value: T) => U): IteratorWrapper&lt;U> {\n        return from(map(this.iter, f));\n    }\n\n    filter(f: (value: T) => boolean): IteratorWrapper&lt;T> {\n        return from(filter(this.iter, f));\n    }\n\n    take(n: number): IteratorWrapper&lt;T> {\n        return from(take(this.iter, n));\n    }\n\n    skip(n: number): IteratorWrapper&lt;T> {\n        return from(skip(this.iter, n));\n    }\n\n    first(): T | undefined {\n        const { value, done } = this.iter.next();\n        return done ? undefined : value;\n    }\n\n    last(): T | undefined {\n        let lastValue: T | undefined = undefined;\n        for (let x of iterableFromIterator(this.iter)) {\n            lastValue = x;\n        }\n        return lastValue;\n    }\n\n    sum(fn: (arg: T) => number): number {\n        let total = 0;\n        for (let x of iterableFromIterator(this.iter)) {\n            total += fn(x);\n        }\n        return total;\n    }\n\n    min(fn: (arg: T) => number): number | undefined {\n        let minValue: number | undefined = undefined;\n        for (let x of iterableFromIterator(this.iter)) {\n            const val = fn(x);\n            if (minValue === undefined || val &lt; minValue) {\n                minValue = val;\n            }\n        }\n        return minValue;\n    }\n\n    max(fn: (arg: T) => number): number | undefined {\n        let maxValue: number | undefined = undefined;\n        for (let x of iterableFromIterator(this.iter)) {\n            const val = fn(x);\n            if (maxValue === undefined || val > maxValue) {\n                maxValue = val;\n            }\n        }\n        return maxValue;\n    }\n    \n    orderBy&lt;U>(fn: (x: T) => U, reverse = false): IteratorWrapper&lt;T> {\n        const arr = this.toArray();\n        const sorted = orderBy(arr, fn, reverse);\n        return from(sorted);\n    }\n\n    orderByDescending&lt;U>(fn: (x: T) => U): IteratorWrapper&lt;T> {\n        return this.orderBy(fn, true);\n    }\n\n    toArray(): T[] {\n        return [...iterableFromIterator(this.iter)];\n    }\n}\n\n<\/pre><\/div>\n\n\n\n<p>Example use:<\/p>\n\n\n\n<div style=\"height: 250px; position:relative; margin-bottom: 50px;\" class=\"wp-block-simple-code-block-ace\"><pre class=\"wp-block-simple-code-block-ace\" style=\"position:absolute;top:0;right:0;bottom:0;left:0\" data-mode=\"typescript\" data-theme=\"monokai\" data-fontsize=\"14\" data-lines=\"Infinity\" data-showlines=\"true\" data-copy=\"false\">const numbers = [1, 2, 3, 4, 5];\nconst result = from(numbers)\n    .map(x => x * 2)\n    .filter(x => x > 5)\n    .take(2)\n    .toArray();\n\nconsole.log(result); \/\/ [6, 8]\n\n\n\nconst values = from([1, 2, 3, 4, 5]);\n\nconsole.log(values.skip(2).toArray());        \/\/ [3, 4, 5]\nconsole.log(from([1, 2, 3]).first());         \/\/ 1\nconsole.log(from([1, 2, 3]).last());          \/\/ 3\nconsole.log(from([1, 2, 3]).sum(x => x));     \/\/ 6\nconsole.log(from([1, 2, 3]).min(x => x));     \/\/ 1\nconsole.log(from([1, 2, 3]).max(x => x));     \/\/ 3\n<\/pre><\/div>\n\n\n\n<p>Generated javascript<\/p>\n\n\n\n<div style=\"height: 250px; position:relative; margin-bottom: 50px;\" class=\"wp-block-simple-code-block-ace\"><pre class=\"wp-block-simple-code-block-ace\" style=\"position:absolute;top:0;right:0;bottom:0;left:0\" data-mode=\"javascript\" data-theme=\"monokai\" data-fontsize=\"14\" data-lines=\"Infinity\" data-showlines=\"true\" data-copy=\"false\">\"use strict\";\nfunction from(iterable) {\n    return new IteratorWrapper(iterable);\n}\nfunction* map(iter, f) {\n    for (let x of iterableFromIterator(iter)) {\n        yield f(x);\n    }\n}\nfunction* filter(iter, f) {\n    for (let x of iterableFromIterator(iter)) {\n        if (f(x))\n            yield x;\n    }\n}\nfunction* take(iter, n) {\n    let i = 0;\n    for (let x of iterableFromIterator(iter)) {\n        if (i++ &lt; n)\n            yield x;\n        else\n            break;\n    }\n}\nfunction* skip(iter, n) {\n    let i = 0;\n    for (let x of iterableFromIterator(iter)) {\n        if (i++ >= n)\n            yield x;\n    }\n}\n\nfunction iterableFromIterator(iter) {\n    return {\n        [Symbol.iterator]() {\n            return iter;\n        }\n    };\n}\nclass IteratorWrapper {\n    constructor(iterable) {\n        this.iter = iterable[Symbol.iterator]();\n    }\n    [Symbol.iterator]() {\n        return this.iter;\n    }\n    map(f) {\n        return from(map(this.iter, f));\n    }\n    filter(f) {\n        return from(filter(this.iter, f));\n    }\n    take(n) {\n        return from(take(this.iter, n));\n    }\n    skip(n) {\n        return from(skip(this.iter, n));\n    }\n    first() {\n        const { value, done } = this.iter.next();\n        return done ? undefined : value;\n    }\n    last() {\n        let lastValue = undefined;\n        for (let x of iterableFromIterator(this.iter)) {\n            lastValue = x;\n        }\n        return lastValue;\n    }\n    sum(fn) {\n        let total = 0;\n        for (let x of iterableFromIterator(this.iter)) {\n            total += fn(x);\n        }\n        return total;\n    }\n    min(fn) {\n        let minValue = undefined;\n        for (let x of iterableFromIterator(this.iter)) {\n            const val = fn(x);\n            if (minValue === undefined || val &lt; minValue) {\n                minValue = val;\n            }\n        }\n        return minValue;\n    }\n    max(fn) {\n        let maxValue = undefined;\n        for (let x of iterableFromIterator(this.iter)) {\n            const val = fn(x);\n            if (maxValue === undefined || val > maxValue) {\n                maxValue = val;\n            }\n        }\n        return maxValue;\n    }\n    toArray() {\n        return [...iterableFromIterator(this.iter)];\n    }\n}\nconst numbers = [1, 2, 3, 4, 5];\nconst result = from(numbers)\n    .map(x => x * 2)\n    .filter(x => x > 5)\n    .take(2)\n    .toArray();\nconsole.log(result); \/\/ [6, 8]\nconst values = from([1, 2, 3, 4, 5]);\nconsole.log(values.skip(2).toArray()); \/\/ [3, 4, 5]\nconsole.log(from([1, 2, 3]).first()); \/\/ 1\nconsole.log(from([1, 2, 3]).last()); \/\/ 3\nconsole.log(from([1, 2, 3]).sum(x => x)); \/\/ 6\nconsole.log(from([1, 2, 3]).min(x => x)); \/\/ 1\n\n<\/pre><\/div>\n","protected":false},"excerpt":{"rendered":"<p>Example use: Generated javascript<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"inline_featured_image":false,"footnotes":""},"categories":[1],"tags":[],"class_list":["post-9465","post","type-post","status-publish","format-standard","hentry","category-uncategorized"],"_links":{"self":[{"href":"https:\/\/solidt.eu\/site\/wp-json\/wp\/v2\/posts\/9465","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/solidt.eu\/site\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/solidt.eu\/site\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/solidt.eu\/site\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/solidt.eu\/site\/wp-json\/wp\/v2\/comments?post=9465"}],"version-history":[{"count":5,"href":"https:\/\/solidt.eu\/site\/wp-json\/wp\/v2\/posts\/9465\/revisions"}],"predecessor-version":[{"id":10025,"href":"https:\/\/solidt.eu\/site\/wp-json\/wp\/v2\/posts\/9465\/revisions\/10025"}],"wp:attachment":[{"href":"https:\/\/solidt.eu\/site\/wp-json\/wp\/v2\/media?parent=9465"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/solidt.eu\/site\/wp-json\/wp\/v2\/categories?post=9465"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/solidt.eu\/site\/wp-json\/wp\/v2\/tags?post=9465"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}