一行 JavaScript 代码(收集)

资料来源于网络

var rate =1;”★★★★★☆☆☆☆☆”.slice(5 - rate, 10 - rate);

“★☆☆☆☆”

(!(~+[])+{})[–[~+””][+[]][~+[]] + ~~!+[]]+({}+[])[[~!+[]]~+[]]

(!(~+[])+{})[–[~+””][+[]][~+[]] + ~~!+[]]+({}+[])[[~!+[]]~+[]]

([][[]]+[])[+!![]]+([]+{})[!+[]+!![]]

nb

在stackoverflow查询有关jssomething的信息
try {
something
} catch (e) {
window.location.href =
http://stackoverflow.com/search?q=[js]+“ + e.message;
}

将页面上所有元素用线框框起来

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[].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

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Array.prototype.forEach.call(document.querySelectorAll('*'), 
dom => dom.style.outline = `1px solid #${parseInt(Math.random() *
Math.pow(2,24)).toString(16)}`)

论如何优雅的取随机字符串

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Math.random().toString(16).substring(2) 
Math.random().toString(36).substring(2)

(10)“toString” === “10”

true

论如何优雅的取整

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var a = ~~2.33

var b= 2.33 | 0

var c= 2.33 >> 0

如何优雅的实现金钱格式化:1234567890 –> 1,234,567,890

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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

论如何最佳的让两个整数交换数值

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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21474836452147483646交换就失败了。
黑科技办法:

a ^= b;
b ^= a;
a ^= b;


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var a = 2147483647,b = 2147483646
a ^= b;
b ^= a;
a ^= b;

实现标准JSON的深拷贝

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var a = {
a: 1,
b: { c: 1, d: 2 }
}
var b=JSON.parse(JSON.stringify(a))

不用Number、parseInt和parseFloat和方法把”1”字符串转换成数字

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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

1

hello world! >

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++[[]][+[]]+[+[]] == 10

true

最短的代码实现数组去重

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[...new Set([1, "1", 2, 1, 1, 3])]

用最短的代码实现一个长度为m(6)且值都n(8)的数组

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Array(6).fill(8)

短路表达式

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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
}

取出一个数组中的最大值和最小值

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var numbers = [5, 458 , 120 , -215 , 228 , 400 , 122205, -85411]; 
var maxInNumbers = Math.max.apply(Math, numbers);
var minInNumbers = Math.min.apply(Math, numbers);

将argruments对象转换成数组

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var argArray = Array.prototype.slice.call(arguments);

或者ES6:

var argArray = Array.from(arguments)

javascript高逼格之Function构造函数

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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

从一个数组中找到一个数,O(n)的算法,找不到就返回 null。

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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))


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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))

object 2 json

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let foo = { a: 2, b: {c:1,d:2} };
JSON.stringify(foo);
"{"a":2,"b":{"c":1,"d":2}}"
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