27 lines
623 B
Markdown
27 lines
623 B
Markdown
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---
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title: "[].map(parseInt)"
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date: 2021-02-14T11:30:00
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---
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Fun fact: `[0xa, 0xa, 0xa].map(parseInt)` yields `[10, NaN, 2]`.
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# Why
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```js
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parseInt(0xa, 0, [0xa, 0xa, 0xa]);
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```
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The second argument is `0` so the first argument going to be treated as decimal number becoming `10`.
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```js
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parseInt(0xa, 1, [0xa, 0xa, 0xa]);
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```
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The second argument is `1` which is invalid as a radix, so the result ends up with `NaN`.
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```js
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parseInt(0xa, 2, [0xa, 0xa, 0xa]);
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```
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The second argument is `2` meaning the first argument going to be handled as a binary number. `0xa` is `10` in binary, which results in `2` in decimal form.
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