你不需要jQuery。您可以使用Javascript 字符串和数组函数。

You don't need jQuery for this. You can use Javascript string and array functions.

1. 按分割字符串。，分隔不同的句子


2. 修剪每个句子


3. 首字母大写字母


4. 按加入。

1. Split the string by ., to separate different sentences
2. Trim each sentence
3. Capitalize first letter
4. Join by .

var str = 'this is a test. this is one more test. and this also new test.';

var newStr = str.split('.').map(function(el) {
  el = el.trim();
  return el.substr(0, 1).toUpperCase() + el.substr(1);
}).join('. ');

alert(newStr.trim());