30秒学会 JavaScript 片段 – mapString

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

Use String.prototype.split('') and Array.prototype.map() to call the provided function, fn, for each character in str.
Use Array.prototype.join('') to recombine the array of characters into a string.
The callback function, fn, takes three arguments (the current character, the index of the current character and the string mapString was called upon).

代码片段

const mapString = (str, fn) =>
  str
    .split('')
    .map((c, i) => fn(c, i, str))
    .join('');

使用样例

mapString('lorem ipsum', c => c.toUpperCase()); // 'LOREM IPSUM'