34 lines
975 B
Markdown
34 lines
975 B
Markdown
---
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title: Calculate SHA-256 hash (Node.js)
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tags: node,promise
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cover: padlocks
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firstSeen: 2018-01-17T14:09:01+02:00
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lastUpdated: 2021-10-13T19:29:39+02:00
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---
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Creates a hash for a value using the [SHA-256](https://en.wikipedia.org/wiki/SHA-2) algorithm.
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Returns a promise.
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- Use `crypto.createHash()` to create a `Hash` object with the appropriate algorithm.
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- Use `hash.update()` to add the data from `val` to the `Hash`, `hash.digest()` to calculate the digest of the data.
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- Use `setTimeout()` to prevent blocking on a long operation. Return a `Promise` to give it a familiar interface.
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```js
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const crypto = require('crypto');
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const hashNode = val =>
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new Promise(resolve =>
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setTimeout(
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() => resolve(crypto.createHash('sha256').update(val).digest('hex')),
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0
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)
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);
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```
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```js
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hashNode(JSON.stringify({ a: 'a', b: [1, 2, 3, 4], foo: { c: 'bar' } })).then(
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console.log
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);
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// '04aa106279f5977f59f9067fa9712afc4aedc6f5862a8defc34552d8c7206393'
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```
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