8ee50178f3
Correct: `Array.from()` (it’s a static method) Incorrect: `Array.join()` (doesn’t exist; it’s a prototype method) This patch uses the common `#` syntax to denote `.prototype.`.
20 lines
680 B
Markdown
20 lines
680 B
Markdown
### mapString
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Creates a new string with the results of calling a provided function on every character in the calling string.
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Use `String.prototype.split('')` and `Array.prototype.map()` to call the provided function, `fn`, for each character in `str`.
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Use `Array.prototype.join('')` to recombine the array of characters into a string.
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The callback function, `fn`, takes three arguments (the current character, the index of the current character and the string `mapString` was called upon).
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```js
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const mapString = (str, fn) =>
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str
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.split('')
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.map((c, i) => fn(c, i, str))
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.join('');
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```
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```js
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mapString('lorem ipsum', c => c.toUpperCase()); // 'LOREM IPSUM'
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```
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