Swapcase string

JavaScript, String · Nov 15, 2020

Creates a string with uppercase characters converted to lowercase and vice versa.

Use the spread operator (...) to convert str into an array of characters.
Use String.prototype.toLowerCase() and String.prototype.toUpperCase() to convert lowercase characters to uppercase and vice versa.
Use Array.prototype.map() to apply the transformation to each character, Array.prototype.join() to combine back into a string.
Note that it is not necessarily true that swapCase(swapCase(str)) === str.

const swapCase = str =>
  [...str]
    .map(c => (c === c.toLowerCase() ? c.toUpperCase() : c.toLowerCase()))
    .join('');

swapCase('Hello world!'); // 'hELLO WORLD!'

Creates a new string with the results of calling a provided function on every character in the given string.

JavaScript, String · Oct 21, 2020

Converts a string to an array of characters.

JavaScript, String · Oct 8, 2020

Converts a comma-separated values (CSV) string to a 2D array of objects. The first row of the string is used as the title row.

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