这些的JavaScript编程黑科技，装逼指南，高逼格代码，让你惊叹不已
原文地址：https://zhuanlan.zhihu.com/p/28937831
Javascript是一门很吊的语言 \n
本文秉承着：你看不懂是你SB，我写的代码就要牛逼。\n\n
1.单行写一个评级组件
"★★★★★☆☆☆☆☆".slice(5 - rate, 10 - rate);
定义一个变量率是1到5的值，然后执行上面代码，看图
才发现插件什么的都弱爆了\n\n## 2.如何装逼用代码骂别人SB
(!(~+[])+{})[--[~+""][+[]]*[~+[]] + ~~!+[]]+({}+[])[[~!+[]]*~+[]]
3.如何用代码优雅的证明自己NB
console.log(([][[]]+[])[+!![]]+([]+{})[!+[]+!![]])
4.JavaScript错误处理的方式的正确姿势
try {
something
} catch (e) {
window.location.href = "http://stackoverflow.com/search?q=[js]+" + e.message;
}
5.从一行代码里面学点JavaScript
[].forEach.call($$("*"),function(a){
a.style.outline="1px solid #"+(~~(Math.random()*(1<<24))).toString(16)
})
翻译成正常语言就是这样的
Array.prototype.forEach.call(document.querySelectorAll('*'),
dom => dom.style.outline = `1px solid #${parseInt(Math.random() * Math.pow(2,24)).toString(16)}`)
接下来在浏览器控制看看：something magic happens
6.论如何优雅的取随机字符串
Math.random().toString(16).substring(2)
Math.random().toString(36).substring(2)
7.(10)"toString" === "10"
8.匿名函数自执行
这么多写法你选择哪一种？
( function() {}() );
( function() {} )();
[ function() {}() ];
~ function() {}();
! function() {}();
+ function() {}();
- function() {}();
delete function() {}();
typeof function() {}();
void function() {}();
new function() {}();
new function() {};
var f = function() {}();
1, function() {}();
1 ^ function() {}();
1 > function() {}();
// ...
9.另外一种undefined
从来不需要声明一个变量的值是undefined，因为JavaScript会自动把一个未赋值的变量置为undefined。所有如果你在代码里这么写，会被鄙视的
var data = undefined;
但是如果你就是强迫症发作，一定要再声明一个暂时没有值的变量的时候赋上一个undefined。那你可以考虑这么做：
var data = void 0; // undefined
void在JavaScript中是一个操作符，对传入的操作不执行并且返回undefined。void后面可以跟()来用，例如void(0)，看起来是不是很熟悉？没错，在HTML里阻止带href的默认点击操作时，都喜欢把href写成javascript:void(0)，实际上也是依靠void操作不执行的意思。
当然，除了出于装逼的原因外，实际用途上不太赞成使用void，因为void的出现是为了兼容早起ECMAScript标准中没有undefined属性。void 0的写法让代码晦涩难懂。
10.论如何优雅的取整
var a = ~~2.33
var b= 2.33 | 0
var c= 2.33 >> 0
11.如何优雅的实现金钱格式化：1234567890 --> 1,234,567,890
用正则魔法实现：
var test1 = '1234567890'
var format = test1.replace(/\\B(?=(\\d{3})+(?!\\d))/g, ',')
console.log(format) // 1,234,567,890
非正则的优雅实现：
function formatCash(str) {
return str.split('').reverse().reduce((prev, next, index) => {
return ((index % 3) ? next : (next + ',')) + prev
})
}
console.log(formatCash('1234567890')) // 1,234,567,890
12.这个我服，还有这个你很机智
while (1) {
alert('牛逼你把我关了啊')
}
好一个障眼法
<a href="javascript:alert('清除成功');">清除缓存</a>
13.逗号运算符
var a = 0;
var b = ( a++, 99 );
console.log(a); // 1
console.log(b); // 99
14.论如何最佳的让两个整数交换数值
常规办法：
var a=1,b=2;
a += b;
b = a - b;
a -= b;
缺点也很明显，整型数据溢出，对于32位字符最大表示数字是2147483647，如果是2147483645和2147483646交换就失败了。
黑科技办法：
a ^= b;
b ^= a;
a ^= b;
15.实现标准JSON的深拷贝
a: 1,
b: { c: 1, d: 2 }
}
var b=JSON.parse(JSON.stringify(a))
不考虑IE的情况下，标准JSON格式的对象蛮实用，不过对于undefined和function的会忽略掉。
16.不用Number、parseInt和parseFloat和方法把"1"字符串转换成数字
哈哈，不准用强制类型转换，那么就想到了强大了隐式转换
var a =1
+a
17.如何装逼的写出"hello world!"
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牛逼的隐式转换
18. parseInt(0.0000008) === 8
19. ++[[]][+[]]+[+[]] == 10
20. 0.1 + 0.2 == 0.3
0.1 +0.2 == 0.3 竟然是不成立的。。。。所以这就是为什么数据库存储对于货币的最小单位都是分。
1.简单说，0.1和0.2的二进制浮点表示都不是精确的，所以相加后不是0.3，接近（不等于）
0.30000000000000004。
所以，比较数字时，应该有个宽容值。ES6中这个宽容值被预定义了：Number.EPSILON。
21. 最短的代码实现数组去重
[...new Set([1, "1", 2, 1, 1, 3])]
22. 用最短的代码实现一个长度为m(6)且值都n(8)的数组
Array(6).fill(8)
23. 短路表达式
条件判断
var a = b && 1
// 相当于
if (b) {
a = 1
} else {
a = b
}
var a = b || 1
// 相当于
if (b) {
a = b
} else {
a = 1
}
24. JavaScript版迷宫
25. 取出一个数组中的最大值和最小值
var numbers = [5, 458 , 120 , -215 , 228 , 400 , 122205, -85411];
var maxInNumbers = Math.max.apply(Math, numbers);
var minInNumbers = Math.min.apply(Math, numbers);
26、将argruments对象转换成数组
var argArray = Array.prototype.slice.call(arguments);
或者ES6：
var argArray = Array.from(arguments)
27、javascript高逼格之Function构造函数
很多JavaScript教程都告诉我们，不要直接用内置对象的构造函数来创建基本变量，例如var arr = new Array(2); 的写法就应该用var arr = [1, 2];的写法来取代。
但是，Function构造函数（注意是大写的Function）有点特别。Function构造函数接受的参数中，第一个是要传入的参数名，第二个是函数内的代码（用字符串来表示）。
var f = new Function('a', 'alert(a)');
f('jawil'); // 将会弹出窗口显示jawil
这种方式可以根据传入字符串内容来创建一个函数 是不是高大上？！
28、从一个数组中找到一个数，O(n)的算法，找不到就返回 null。
正常的版本:
function find (x, y) {
for ( let i = 0; i < x.length; i++ ) {
if ( x[i] == y ) return i;
}
return null;
}
let arr = [0,1,2,3,4,5]
console.log(find(arr, 2))
console.log(find(arr, 8))
结果到了函数式成了下面这个样子（好像上面的那些代码在下面若影若现，不过又有点不太一样，为了消掉if语言，让其看上去更像一个表达式，动用了 ? 号表达式）：
//函数式的版本
const find = ( f => f(f) ) (
f => (
next => (
x,
y,
i = 0
) => (
i >= x.length
) ? null : (
x[i] == y
) ? i : next(
x,
y,
i+1
)
)(
(
...args
) => (
f(f)
)(...args)
)
)
let arr = [0,1,2,3,4,5]
console.log(find(arr, 2))
console.log(find(arr, 8))
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