freeCodeCamp/curriculum/challenges/chinese/02-javascript-algorithms-and-data-structures/basic-algorithm-scripting/truncate-a-string.md

id, title, challengeType, forumTopicId, dashedName

id	title	challengeType	forumTopicId	dashedName
ac6993d51946422351508a41	截断字符串	5	16089	truncate-a-string

--description--

如果传入的字符串（第一个参数）的长度大于传入的值（第二个参数），请在这个位置截断它并在后面加上 ...，然后返回结果。

--hints--

truncateString("A-tisket a-tasket A green and yellow basket", 8) 应返回 "A-tisket..."。

assert(
  truncateString('A-tisket a-tasket A green and yellow basket', 8) ===
    'A-tisket...'
);

truncateString("Peter Piper picked a peck of pickled peppers", 11) 应返回 "Peter Piper..."。

assert(
  truncateString('Peter Piper picked a peck of pickled peppers', 11) ===
    'Peter Piper...'
);

truncateString("A-tisket a-tasket A green and yellow basket", "A-tisket a-tasket A green and yellow basket".length) 应返回 "A-tisket a-tasket A green and yellow basket"。

assert(
  truncateString(
    'A-tisket a-tasket A green and yellow basket',
    'A-tisket a-tasket A green and yellow basket'.length
  ) === 'A-tisket a-tasket A green and yellow basket'
);

truncateString("A-tisket a-tasket A green and yellow basket", "A-tisket a-tasket A green and yellow basket".length + 2) 应返回 "A-tisket a-tasket A green and yellow basket"。

assert(
  truncateString(
    'A-tisket a-tasket A green and yellow basket',
    'A-tisket a-tasket A green and yellow basket'.length + 2
  ) === 'A-tisket a-tasket A green and yellow basket'
);

truncateString("A-", 1) 应返回 "A..."。

assert(truncateString('A-', 1) === 'A...');

truncateString("Absolutely Longer", 2) 应返回 "Ab..."。

assert(truncateString('Absolutely Longer', 2) === 'Ab...');

--seed--

--seed-contents--

function truncateString(str, num) {
  return str;
}

truncateString("A-tisket a-tasket A green and yellow basket", 8);

--solutions--

function truncateString(str, num) {
  if (num >= str.length) {
    return str;
  }

  return str.slice(0, num) + '...';
}

truncateString("A-tisket a-tasket A green and yellow basket", 8);