38 lines
1.4 KiB
Markdown
38 lines
1.4 KiB
Markdown
---
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title: Calculate SHA-256 hash (browser)
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type: snippet
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language: javascript
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tags: [browser,promise]
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cover: padlocks
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dateModified: 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 the [SubtleCrypto](https://developer.mozilla.org/en-US/docs/Web/API/SubtleCrypto) API to create a hash for the given value.
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- Create a new `TextEncoder` and use it to encode `val`. Pass its value to `SubtleCrypto.digest()` to generate a digest of the given data.
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- Use `DataView.prototype.getUint32()` to read data from the resolved `ArrayBuffer`.
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- Convert the data to its hexadecimal representation using `Number.prototype.toString()`. Add the data to an array using `Array.prototype.push()`.
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- Finally, use `Array.prototype.join()` to combine values in the array of `hexes` into a string.
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```js
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const hashBrowser = val =>
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crypto.subtle
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.digest('SHA-256', new TextEncoder('utf-8').encode(val))
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.then(h => {
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let hexes = [],
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view = new DataView(h);
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for (let i = 0; i < view.byteLength; i += 4)
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hexes.push(('00000000' + view.getUint32(i).toString(16)).slice(-8));
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return hexes.join('');
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});
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```
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```js
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hashBrowser(
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JSON.stringify({ a: 'a', b: [1, 2, 3, 4], foo: { c: 'bar' } })
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).then(console.log);
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// '04aa106279f5977f59f9067fa9712afc4aedc6f5862a8defc34552d8c7206393'
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```
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