plimit.js

commit 8490f64ef14154e42b03896e356bf576d90ea9d3
Author: Robin Bron <finwo@pm.me>
Date:   Fri, 10 Dec 2021 10:46:23 +0100

Project init

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README.html
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README.md
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index.js
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package.json
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4 files changed, 127 insertions(+), 0 deletions(-)
diff --git a/README.html b/README.html
@@ -0,0 +1,38 @@
+<h1>plimit</h1>
+<p>Simple promise concurrency limiter</p>
+<h2>Installation</h2>
+<pre><code class="language-sh">npm install --save plimit
+</code></pre>
+<pre><code class="language-js"># node
+import { plimit } from 'plimit';
+</code></pre>
+<pre><code class="language-html">&lt;!-- browser --&gt;
+&lt;script src=&quot;/path/to/plimit/index.js&quot;&gt;&lt;/script&gt;
+&lt;script&gt;
+  // use window.plimit
+&lt;/script&gt;
+</code></pre>
+<h2>Usage</h2>
+<p>The package assumes native promises are available</p>
+<p>This example shows iterating over accounts without loading all into memory</p>
+<pre><code class="language-js">import { MoreThan } from 'typeorm';
+import { Account } from './model/account'; // typescript model
+
+const runner    = plimit(4); // runner that allows 4 concurrent tasks
+let   accountId = '';
+
+while(true) {
+  const account = await Account.findOne({ uuid: MoreThan(accountId) });
+  if (!account) break;
+  accountId = account.uuid;
+
+  // resolves instantly it's queue is not full
+  // waits for a previous task if it's queue is full
+  await runner.push(async () =&gt; {
+    // some lengthy process on the account
+  });
+}
+
+// Process remainder
+await runner.flush();
+</code></pre>
diff --git a/README.md b/README.md
@@ -0,0 +1,51 @@
+# plimit
+
+Simple promise concurrency limiter
+
+## Installation
+
+```sh
+npm install --save @finwo/p-limit
+```
+
+```js
+# node
+import { plimit } from 'plimit';
+```
+
+```html
+<!-- browser -->
+<script src="/path/to/plimit/index.js"></script>
+<script>
+  // use window.plimit
+</script>
+```
+
+## Usage
+
+The package assumes native promises are available
+
+This example shows iterating over accounts without loading all into memory
+
+```js
+import { MoreThan } from 'typeorm';
+import { Account } from './model/account'; // typescript model
+
+const runner    = plimit(4); // runner that allows 4 concurrent tasks
+let   accountId = '';
+
+while(true) {
+  const account = await Account.findOne({ uuid: MoreThan(accountId) });
+  if (!account) break;
+  accountId = account.uuid;
+
+  // resolves instantly it's queue is not full
+  // waits for a previous task if it's queue is full
+  await runner.push(async () => {
+    // some lengthy process on the account
+  });
+}
+
+// Process remainder
+await runner.flush();
+```
diff --git a/index.js b/index.js
@@ -0,0 +1,26 @@
+(factory => {
+  if ('object' === typeof module) {
+    module.exports = factory();
+  } else if ('object' === typeof window) {
+    Object.assign(window, factory());
+  } else {
+    throw new Error("Neither 'module.exports' nor 'window' exist");
+  }
+})(() => ({
+  plimit(concurrency) {
+    const queue = [];
+    return {
+      push(task) {
+        queue.push(task);
+        if (queue.length >= concurrency) {
+          return queue.shift();
+        } else {
+          return Promise.resolve();
+        }
+      },
+      async flush() {
+        while(queue.length) await queue.shift();
+      },
+    };
+  }
+}));
diff --git a/package.json b/package.json
@@ -0,0 +1,12 @@
+{
+  "name": "@finwo/p-limit",
+  "version": "1.0.0",
+  "description": "",
+  "main": "index.js",
+  "scripts": {
+    "test": "echo \"Error: no test specified\" && exit 1"
+  },
+  "keywords": [],
+  "author": "",
+  "license": "ISC"
+}