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📚积累前端知识

JavaScript 95.84% HTML 4.16%

css es6 git http javascript mac react rxjs vim vscode

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扑克牌问题

背景

手中有一堆扑克牌，不知道它的顺序。
第一步，从牌顶拿出一张牌，放到桌子上。
第二步，从牌顶再拿一张牌，放在手上牌的底部。
第三步，重复第一步、第二步的操作，直到手中所有的牌都放到了桌子上。
最后，桌子上牌的顺序是：(牌底部）1,2,3,4,5,6,7,8,9,10,11,12,13(牌顶部）
请问，刚开始拿在手里的牌的顺序是什么？

思路：

首先，这扑克牌问题主要考察逆向思维，就是先告诉我们结果，然后让我们顺藤摸瓜，一步一步到达开始。

写个简单例子：

var a = [1, 2, 3, 4, 5];
function f(a){
    let b = [],
	c = [...a],
	len = a.length;
    for(let i = 0; i < len; i++){
	b.push(c.pop());
	c.unshift(c.pop());
    }
    return b;
}
f(a);  // b ==> [5, 3, 1, 2, 4];

这个例子是按照正向思维实现的，可是题目的要求，只给到我们b的的值，a的值是不知道的，有点像数学里面的求解函数。因此，我们只需要调整for循环里面的取值顺序，就能轻松解开。

var a = [5, 3, 1, 2, 4];
function f(a){
    let b = [],
	c = [...a],
	len = a.length;
    for(let i = 0; i < len; i++){
	b.push(c.pop());
	b.push(b.shift());
    }
    b.unshift(b.pop());
    return b;
}
f(a);  // b ==> [1, 2, 3, 4, 5]

最后规范一下命名，增强可读性。

/**
 * Input 拿出牌的顺序 1,2,3,4,5,6,7,8,9,10,11,12,13
 * Output 牌堆原来的顺序
 */
function getCardsOrder(input){
    let output = [],
        copyInput = [...input],
        len = input.length;
    for(let i = 0; i < len; i++){
        output.push(copyInput.pop());
        output.push(output.shift());
    }
    output.unshift(output.pop());
    return output;
}

Git流程

A successful Git branching model

React的生命周期理解

http://projects.wojtekmaj.pl/react-lifecycle-methods-diagram/

JavaScript函数和React源码

// 斐波那契函数

function fibonacci(num)｛
    if(num === 1 || num === 2)｛
        return 1;
    ｝
    return fibonacci(num - 1) + fibonacci(num - 2);
｝

===

(0.8 + 0.7 + 0.6 + 0.9) / 4 // 0.75
(0.6 + 0.8 + 0.7 + 0.9) / 4 // 0.7499999999999999

(6 + 8 + 7 + 9) / 4 // 7.5
(8 + 7 + 6 + 9) / 4 // 7.5

在字典中最好使用整数值

Webpack和按需加载

webpack-chart: webpack 数据交互饼图

链接：https://alexkuz.github.io/webpack-chart/

按需加载

链接：eyasliu/blog#8

Commit Message Emoji

commit-message-emoji

Commit type	Emoji
Initial commit	🎉 `:tada:`
Version tag	🔖 `:bookmark:`
New feature	✨ `:sparkles:`
Bugfix	🐛 `:bug:`
Metadata	📇 `:card_index:`
Documentation	📚 `:books:`
Documenting source code	💡 `:bulb:`
Performance	🐎 `:racehorse:`
Cosmetic	💄 `:lipstick:`
Tests	🚨 `:rotating_light:`
Adding a test	✅ `:white_check_mark:`
General update	⚡ `:zap:`
Improve format/structure	🎨 `:art:`
Refactor code	🔨 `:hammer:`
Removing code/files	🔥 `:fire:`
Continuous Integration	💚 `:green_heart:`
Security	🔒 `:lock:`
Upgrading dependencies	⬆️ `:arrow_up:`
Downgrading dependencies	⬇️ `:arrow_down:`
Lint	👕 `:shirt:`
Translation	👽 `:alien:`
Text	📝 `:pencil:`
Critical hotfix	🚑 `:ambulance:`
Deploying stuff	🚀 `:rocket:`
Fixing on MacOS	🍎 `:apple:`
Fixing on Linux	🐧 `:penguin:`
Fixing on Windows	🏁 `:checkered_flag:`
Work in progress	🚧 `:construction:`
Adding CI build system	👷 `:construction_worker:`
Analytics or tracking code	📈 `:chart_with_upwards_trend:`
Removing a dependency	➖ `:heavy_minus_sign:`
Adding a dependency	➕ `:heavy_plus_sign:`
Docker	🐳 `:whale:`
Configuration files	🔧 `:wrench:`
Package.json in JS	📦 `:package:`
Merging branches	🔀 `:twisted_rightwards_arrows:`
Bad code / need improv.	💩 `:hankey:`
Reverting changes	⏪ `:rewind:`
Breaking changes	💥 `:boom:`
Code review changes	👌 `:ok_hand:`
Accessibility	♿ `:wheelchair:`
Move/rename repository	🚚 `:truck:`
Other	Be creative