???? 前言
大家好呀，我是毛小悠，能够叫我二毛，在家中排行老二，是一名前端开发工程师。
本系列文章旨在通过练习来进步JavaScript的能力，一起欢快的做题吧。????????????
以下每道题，二毛我都有尝试做一遍。倡议限时训练，比方限定为半小时，如果半小时内想不进去，能够联合文章开端的参考答案来思考。
能够在下方评论区留言或者加我的微信：code_maomao。期待你的到来。
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???? 题目1：用函数计算
这次咱们要应用函数编写计算并取得后果。让咱们看一些例子：
seven(times(five())); // must return 35four(plus(nine())); // must return 13eight(minus(three())); // must return 5six(dividedBy(two())); // must return 3要求：
- 每个数字必须有一个函数，范畴从0（“零”）到9（“ 9”）
- 以下每个数学运算必须具备一个函数：加，减，乘，除（
divided_by在Ruby和Python中） - 每次计算仅由一个操作和两个数字组成
- 最外层的函数代表左操作数，最内层的函数代表右操作数
- 除法应为整体除法。例如，应返回2，而不是2.666666...
eight(dividedBy(three()));习题代码
function zero() {}function one() {}function two() {}function three() {}function four() {}function five() {}function six() {}function seven() {}function eight() {}function nine() {}function plus() {}function minus() {}function times() {}function dividedBy() {}???? 题目2：RGB到十六进制转换
rgb性能不残缺。把RGB十进制值变为十六进制示意模式。RGB的无效十进制转换0-255。任何超出该范畴的值都必须四舍五入为最靠近的有效值。留神：您的答案应始终为6个字符长，带有3个字符的#FFF速记在这里不起作用。
以下是预期输入值的示例：
rgb(255, 255, 255) // returns FFFFFFrgb(255, 255, 300) // returns FFFFFFrgb(0,0,0) // returns 000000rgb(148, 0, 211) // returns 9400D3习题代码：
rgb(r,g,b){}???? 题目3：谁喜爱呢？
您可能从Facebook和其余页面晓得“喜爱”机制。
实现一个函数likes :: [String] -> String
likes [] -- must be "no one likes this"likes ["Peter"] -- must be "Peter likes this"likes ["Jacob", "Alex"] -- must be "Jacob and Alex like this"likes ["Max", "John", "Mark"] -- must be "Max, John and Mark like this"likes ["Alex", "Jacob", "Mark", "Max"] -- must be "Alex, Jacob and 2 others like this"对于4个或更多的名称，数字and 2 others
习题代码
function likes(names) { // TODO}答案
???? 题目1的答案
参考答案1：
var n = function(digit) { return function(op) { return op ? op(digit) : digit; }};var zero = n(0);var one = n(1);var two = n(2);var three = n(3);var four = n(4);var five = n(5);var six = n(6);var seven = n(7);var eight = n(8);var nine = n(9);function plus(r) { return function(l) { return l + r; }; }function minus(r) { return function(l) { return l - r; }; }function times(r) { return function(l) { return l * r; }; }function dividedBy(r) { return function(l) { return l / r; }; }参考答案2：
function zero(func) { return func ? func(0) : 0; };function one(func) { return func ? func(1) : 1; };function two(func) { return func ? func(2) : 2; };function three(func) { return func ? func(3) : 3; };function four(func) { return func ? func(4) : 4; };function five(func) { return func ? func(5) : 5; };function six(func) { return func ? func(6) : 6; };function seven(func) { return func ? func(7) : 7; };function eight(func) { return func ? func(8) : 8; };function nine(func) { return func ? func(9) : 9; };function plus( b ) { return function( a ) { return a + b; }; };function minus( b ) { return function( a ) { return a - b; }; };function times( b ) { return function( a ) { return a * b; }; };function dividedBy( b ) { return function( a ) { return a / b; }; };参考答案3：
['zero', 'one', 'two', 'three', 'four', 'five', 'six', 'seven', 'eight', 'nine'].forEach(function (name, n) { this[name] = function (f) { return f ? f(n) : n }});function plus(n) { return function (a) { return a + n } }function minus(n) { return function (a) { return a - n } }function times(n) { return function (a) { return a * n } }function dividedBy(n) { return function (a) { return a / n } }参考答案4：
'zero one two three four five six seven eight nine'.split(' ').forEach( (mth, num) => this[mth] = (f = val => val) => f(num) )let plus = (r) => (l) => l + rlet minus = (r) => (l) => l - rlet times = (r) => (l) => l * rlet dividedBy = (r) => (l) => l / r参考答案5：
const id = x => x, number = x => (f = id) => f(x), [zero, one, two, three, four, five, six, seven, eight, nine] = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9].map(number), plus = x => y => y + x, minus = x => y => y - x, times = x => y => y * x, dividedBy = x => y => y / x;???? 题目2的答案
参考答案1：
function rgb(r, g, b){ return toHex(r)+toHex(g)+toHex(b);}function toHex(d) { if(d < 0 ) {return "00";} if(d > 255 ) {return "FF";} return ("0"+(Number(d).toString(16))).slice(-2).toUpperCase()}参考答案2：
function rgb(r, g, b){ return [r,g,b].map(function(x) { return ('0'+Math.max(0, Math.min(255, x)).toString(16)).slice(-2); }).join('').toUpperCase();}参考答案3：
function rgb(r, g, b){ function toHex(a) { if (a <= 0) return '00'; else if (a >= 255) return 'FF'; else return a.toString(16).toUpperCase(); } return toHex(r) + toHex(g) + toHex(b);}参考答案4：
const rgb = (r, g, b) => toHex(r) + toHex(g) + toHex(b);function toHex(numb) { if (numb <= 0) return '00'; if (numb > 255) return 'FF'; return numb.toString(16).toUpperCase();}参考答案5：
let rgb = (r, g, b) => [r,g,b].map( (item) => item>=255 ? 'FF' : item<=0 ? '00' : item.toString(16).toUpperCase()).join('')???? 题目3的答案
参考答案1：
function likes(names) { names = names || []; switch(names.length){ case 0: return 'no one likes this'; break; case 1: return names[0] + ' likes this'; break; case 2: return names[0] + ' and ' + names[1] + ' like this'; break; case 3: return names[0] + ', ' + names[1] + ' and ' + names[2] + ' like this'; break; default: return names[0] + ', ' + names[1] + ' and ' + (names.length - 2) + ' others like this'; }}参考答案2：
function likes(names) { return { 0: 'no one likes this', 1: `${names[0]} likes this`, 2: `${names[0]} and ${names[1]} like this`, 3: `${names[0]}, ${names[1]} and ${names[2]} like this`, 4: `${names[0]}, ${names[1]} and ${names.length - 2} others like this`, }[Math.min(4, names.length)]}参考答案3：
function likes (names) { var templates = [ 'no one likes this', '{name} likes this', '{name} and {name} like this', '{name}, {name} and {name} like this', '{name}, {name} and {n} others like this' ]; var idx = Math.min(names.length, 4); return templates[idx].replace(/{name}|{n}/g, function (val) { return val === '{name}' ? names.shift() : names.length; });}参考答案4：
function likes(names) { if(names.length === 0) return "no one likes this"; if(names.length === 1) return names[0] + " likes this"; if(names.length === 2) return names[0] + " and " + names[1] + " like this"; if(names.length === 3) return names[0] + ", " + names[1] + " and " + names[2] + " like this"; return names[0] + ", " + names[1] + " and " + (names.length - 2) + " others like this";}参考答案5：
function likes(names) { switch(names.length){ case 0: return "no one likes this"; case 1: return names[0] + " likes this"; case 2: return names[0] + " and " + names[1] + " like this"; case 3: return names[0] + ", " + names[1] + " and " + names[2] + " like this"; default: return names[0] + ", " + names[1] + " and " + (names.length-2) + " others like this"; }}????后序
本系列会定期更新的，题目会由浅到深的逐步提高。
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