32 lines
924 B
Markdown
32 lines
924 B
Markdown
---
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title: Generate while condition is met
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tags: function,generator
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expertise: advanced
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author: chalarangelo
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cover: blog_images/lake-loop.jpg
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firstSeen: 2022-01-21T05:00:00-04:00
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---
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Creates a generator, that keeps producing new values as long as the given condition is met.
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- Initialize the current `val` using the `seed` value.
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- Use a `while` loop to iterate while the `condition` function called with the current `val` returns `true`.
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- Use `yield` to return the current `val` and optionally receive a new seed value, `nextSeed`.
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- Use the `next` function to calculate the next value from the current `val` and the `nextSeed`.
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```js
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const generateWhile = function* (seed, condition, next) {
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let val = seed;
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let nextSeed = null;
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while (condition(val)) {
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nextSeed = yield val;
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val = next(val, nextSeed);
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}
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return val;
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};
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```
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```js
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[...generateWhile(1, v => v <= 5, v => ++v)]; // [1, 2, 3, 4, 5]
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```
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