repeat()方法的语法为：
str.repeat(count)在这里， str是一个字符串。
repeat()参数
repeat()方法采用：
- count – 0到+ Infinity之间的整数，指示重复字符串的次数。
从repeat()返回值
- 返回一个新字符串，其中包含给定字符串的指定副本数。
注意 ：如果重复计数为负，无穷大或最大字符串大小溢出，则repeat()会引发RangeError 。
示例：使用repeat()方法
let sentence = "Happy Birthday to you! ";
let repeat1 = sentence.repeat(2);
console.log(repeat1); // 'Happy Birthday to you! Happy Birthday to you!'
// count is converted to integer
let repeat2 = sentence.repeat(3.5);
// 'Happy Birthday to you! Happy Birthday to you! Happy Birthday to you!'
console.log(repeat2);
let repeat3 = sentence.repeat(0);
console.log(repeat3); // ''
// RangeError if count is negative or infinite
let repeat4 = sentence.repeat(-1);
console.log(repeat4); // RangeError: Invalid count value输出
Happy Birthday to you! Happy Birthday to you!
Happy Birthday to you! Happy Birthday to you! Happy Birthday to you!
error: Uncaught RangeError: Invalid count value推荐读物： JavaScript String concat()