30秒学会 JavaScript 片段 – Pad string

Pads a string on both sides with the specified character, if it’s shorter than the specified length.

• Use String.prototype.padStart() and String.prototype.padEnd() to pad both sides of the given string.
• Omit the third argument, char, to use the whitespace character as the default padding character.

代码实现

const pad = (str, length, char = ' ') =>
  str.padStart((str.length + length) / 2, char).padEnd(length, char);

pad('cat', 8); // '  cat   '
pad(String(42), 6, '0'); // '004200'
pad('foobar', 3); // 'foobar'

翻译自：https://www.30secondsofcode.org/js/s/pad-string