瞠目结舌的JavaScript技巧

今天在知乎上看到一篇JavaScript技巧，学习并收藏之

1. 快速打印一个五分制的评分情况

function getRating(rating) {

if(rating > 5 || rating < 0) throw new Error(‘数字不在范围内‘);

return ‘★★★★★☆☆☆☆☆‘.substring(5 - rating, 10 - rating );

}

2.拼接重复字符串（abcabcabc）

//输出n个‘abc’拼接的字符串

var str = new Array(n+1).join(‘abc‘);

• false => ![]
• true => !![]
• undefined => [][[]]
• NaN => +[![]]
• 0 => +[]
• 1 => +!+[]
• 2 => !+[]+!+[]
• 10 => [+!+[]]+[+[]]
• Array => []
• Number => +[]
• String => []+[]
• Boolean => ![]
• Function => []["filter"]
• eval => []["filter"]["constructor"]( CODE )()
• window => []["filter"]["constructor"]("return this")()

  来源： <http://www.jsfuck.com/>

来自为知笔记(Wiz)