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javascript/snippets/hash-node.md

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+---
+title: Calculate SHA-256 hash (Node.js)
+type: snippet
+tags: [node,promise]
+cover: padlocks
+dateModified: 2021-10-13T19:29:39+02:00
+---
+
+Creates a hash for a value using the [SHA-256](https://en.wikipedia.org/wiki/SHA-2) algorithm.
+Returns a promise.
+
+- Use `crypto.createHash()` to create a `Hash` object with the appropriate algorithm.
+- Use `hash.update()` to add the data from `val` to the `Hash`, `hash.digest()` to calculate the digest of the data.
+- Use `setTimeout()` to prevent blocking on a long operation. Return a `Promise` to give it a familiar interface.
+
+```js
+const crypto = require('crypto');
+
+const hashNode = val =>
+  new Promise(resolve =>
+    setTimeout(
+      () => resolve(crypto.createHash('sha256').update(val).digest('hex')),
+      0
+    )
+  );
+```
+
+```js
+hashNode(JSON.stringify({ a: 'a', b: [1, 2, 3, 4], foo: { c: 'bar' } })).then(
+  console.log
+);
+// '04aa106279f5977f59f9067fa9712afc4aedc6f5862a8defc34552d8c7206393'
+```