daily CodeWars

每天都在codewars做题，刷题。

记录一下。。

CodeWars

• Javascript filter - 1

  function searchNames(logins){
    return logins.filter(function(login){return /_$/.test(login[0])});
  }
  

• The range() function

  function range(start, end, step) {
  step = step===undefined?1:step;
  if(end===undefined){
   end = start;
   start = 0;
  }
  if(end==0){
   return [];
  }
  var res = [start];
  if(step!=0){
   while(start+stepelse{
   for(var i=2; ireturn res;
  }
  

• Convert a Number to a String!

  function numberToString(num){
    return ''+num;
  }
  

• Who likes it?

  function likes(names) {
  var res='',
      len = names.length;
  switch(len){
    case 0:
      res = 'no one likes this';
      break;
    case 1:
      res = names[0] + " likes this";
      break;
    case 2:
      res = names[0]+" and "+ names[1]+ " like this";
      break;
    case 3:
      res = names[0]+", "+ names[1]+" and "+names[2] + " like this";
      break;
    default:
      res = names[0]+", "+ names[1]+" and "+(names.length-2) +" others like this";
      break;
  }
  return res;
  }
  

• Naughty or Nice?

  function getNiceNames(people){
  return people.filter(function(per){
    return per.wasNice;
  }).map(function(e){return e.name});
  }
  function getNaughtyNames(people){
  return people.filter(function(per){
    return !per.wasNice;
  }).map(function(e){return e.name});
  }
  

• return a sorted list of objects

  function sortList (sortBy, list) {
  return list.sort(function(a, b){return parseInt(b[sortBy])-parseInt(a[sortBy])});
  }
  

• Find the Remainder

  function remainder(a, b){
  return Math.max(a,b)%Math.min(a,b);
  }
  

• Building Strings From a Hash

  function solution(pairs){
                      var re="";
                      for(var i in pairs){
                        re += i+" = "+pairs[i]+','
                      }
                      return re.substring(0,re.length-1);
  }
  

• Array.diff

  //原来还可以用indexOf 来判断数组元素是否存在
  function array_diff(a, b) {
  return a.filter(function(e){return b.indexOf(e)==-1});
  }
  

• No oddities here

  function noOdds( values ){
  return values.filter(function(e){return e%2==0;});
  }
  

• Flatten

  //我的渣做法
  var flatten = function (array){
  var res = [],
     len = array.length;
  for(var i=0;ivar ar = array[i];
   if(ar instanceof Array){
     for(var j=0;jelse{
       res.push(ar);
   }
  }
  return res;
  }
  //优雅做法
  var flatten = function (array){
  return [].concat.apply([],array);
  }
  

• Mr.Freeze

  // mark the MrFreeze object instance as frozen
  Object.freeze(MrFreeze);
  

• Pluck

  function pluck(objs, name) {
  return objs.map(function(obj){
    return obj[name];
  });
  }
  

• Reverse words

  //原来reverse是Array的方法,String是没有的
  function reverseWords(str) {
    return str.split(" ").map(function(a){
     return a.split('').reverse().join('');
   }).join(" ");
  }
  

• Get key/value pairs as arrays

  function keysAndValues(data){
  var keys=[],
      values=[],
      res = [];
  for(var key in data){
    keys.push(key);
    values.push(data[key]);
  }
  res.push(keys);
  res.push(values);
  return res;
  }
  //优雅写法
  function keysAndValues(data){
    return [Object.keys(data)].push(Object.keys(data).map(function(e){return data[e]}));
  }
  

• SantaClausable Interface

  //踩坑点:要判断是否为function
  function isSantaClausable(obj) {
   return (typeof obj.sayHoHoHo =='function')
   &&(typeof obj.distributeGifts == 'function')
   &&(typeof obj.goDownTheChimney == 'function');
  }
  //优雅写法
  function isSantaClausable(obj) {
    return ['sayHoHoHo','distributeGifts','goDownTheChimney'].every(function(m){return typeof obj[m]=='function'});
  }
  

• Disemvowel Trolls

  function disemvowel(str) {
  return str.split('').map(function(e){
    if(['e','i','o','a','u','A','O','E','I','U'].indexOf(e)==-1){
      return e;
    }
  }).join('');
  }
  //best practice
  function disemvowel(str) {
  return str.replace(/[aeiou]/gi, '');
  }
  

• Summing a number's digits

  function sumDigits(number) {
    var sum = 0;
  (number<0?(-number)+'':number+'').split('').forEach(function(e){sum+=parseInt(e)});
  return sum;
  }
  

• Number Of Occurrences

  Array.prototype.numberOfOccurrences = function() {
  if(arguments.length<1){
    return 0;
  }
  var times = 0,
      arg = arguments[0];
  this.forEach(function(e){
    if(e===arg){//argument不能乱用，只能用局部变量暂存
      times++;
    }
  });
  return times;
  }
  //best practice
  Array.prototype.numberOfOccurrences = function(search){
    return this.filter(function(num){return search===num}).length;
  };
  

• Count characters in your string

  function count (string) {  
   var res = {};
   var str = string.split('').forEach(function(e){
     res[e] = res[e]?res[e]+1:1;
   });
   return res;
  }
  

• Reversed Strings

  function solution(str){
  return str.split('').reverse().join('');
  }
  

• Sentence Smash

  function smash (words) {
    "use strict";
    return words.join(' ');
  };
  

• Sort the Gift Code

  function sortGiftCode(code){
  return code.split('').sort().join(''); 
  }
  

• Remove anchor from URL

  function removeUrlAnchor(url){
  return url.split('#')[0];
  }
  

• Basic Training: Add item to an Array

  websites.push('codewars');
  

• Anything to integer

  function toInteger(n) {
  var num = Number(n)+'';
  var t= num.split('\.')[0];
  if(num=='Infinity'||num=='NaN')return 0;
  return Number(t);
  }
  

• Is Integer Array ?

  function isIntArray(arr) {
  return arr instanceof Array?arr.every(function(e){return e!=null &&typeof e != 'string'&&!isNaN(e)&&(e+'').indexOf('.')==-1}):false;
  }
  

• Return substring instance count

  function solution(fullText, searchText){
  return fullText.split(searchText).length-1;
  }
  

• Sort arrays - 1

  sortme = function( names ){
  return names.sort();
  }
  

• Sort arrays - 2

  sortme = function( names ){
   return names.sort(function(a,b){return a.toLowerCase().localeCompare(b.toLowerCase())})
  }
  

• Functional Addition

  function add(n) {
  return function(){
    return arguments[0]+n;
  }
  }
  

• Function 2 - squaring an argument

  function square(e){
  return e*e;
  }
  

• Singleton Pattern

  var Singleton = function(){
  if(Singleton._instance)return Singleton._instance;
  if(!this instanceof Singleton)return new Singleton();
  Singleton._instance = this;
  };
  

• Sentences with Functions

  function Adam() {return arguments[0]?'Adam '+arguments[0]:'Adam.'}
  function has() {return 'has '+arguments[0]}
  function a() {return 'a '+arguments[0]}
  function dog() {return arguments[0]?'dog '+arguments[0]:'dog.'}
  function The() {return 'The '+arguments[0]}
  function name() {return 'name '+arguments[0]}
  function of() {return 'of '+arguments[0]}
  function the() {return 'the '+arguments[0]}
  function is() {return 'is '+arguments[0]}
  function also() {return 'also '+arguments[0]}
  

• Elapsed Seconds

  function elapsedSeconds(startDate, endDate){
  return (Date.parse(endDate)-Date.parse(startDate))/1000;
  }
  

• Trim a String

  String.prototype.trim = function() {
  return this.replace(/^\s*/g,'').replace(/\s*$/g,'');
  };
  

• Square(n) Sum

  function squareSum(numbers){
    return numbers.map(function(e){return e*e}).reduce(function(e1,e2){return e1+e2});
  }
  

• The Coupon Code

  function checkCoupon(enteredCode, correctCode, currentDate, expirationDate){
  if(enteredCode===correctCode){
    return new Date(currentDate)<=new Date(expirationDate);
  }
  return false;
  }
  

• Operator overload ?

  var Foo = function(value) {
  this.val = value;
  }
  Foo.prototype.valueOf = function(){
  return this.val;
  }
  

• JavaScript class-like objects

  function Animal(name, type){
  this.name = name;
  this.type = type;
  this.toString = function(){
    return this.name+' is a '+this.type;
  }
  }
  

• Anagram Detection

  var isAnagram = function(test, original) {
   var tl = original.toLowerCase();
  return test.length==original.length&&test.toLowerCase().split('').every(function(e){return tl.indexOf(e)>-1})
  };
  

• esreveR gnirtS

  String.prototype.reverse = function(){
  return this.split('').reverse().join('');
  }
  

• Basic JS - Calculating averages

  var Calculator = {
  average: function() {
  return arguments.length?Array.prototype.reduce.call(arguments, function(a,b){return a+b})/arguments.length:0;
  }
  };
  

• Numerology

  /**
  * Your solution
  * @date JS Date object
  **/
  function solution(date){
  var sum = (date.getDate()+date.getMonth()+1+date.getFullYear());
  return splitsum(splitsum(sum));
  }
  function splitsum(i){
  return Number((''+i).split('').reduce(function(a,b){return parseInt(a)+parseInt(b)}));
  }
  

• The Vowel Code

  function encode(string){
  return string.replace(/a/g,1).replace(/e/g,2).replace(/i/g,3).replace(/o/g,4).replace(/u/,5);
  }
  //turn numbers back into vowels
  function decode(string){
  return string.replace(/1/g,'a').replace(/2/g,'e').replace(/3/g,'i').replace(/4/g,'o').replace(/5/,'u');
  }
  

• Number-like counter

  function Counter(){
  this.val=0;
  this.valueOf =function(){return this.val;}
  }
  Counter.prototype.incr = function() {
  return ++this.val;
  }
  

• Name Array Capping

  function capMe(names) {
  return names.map(function(e){
   return e.substr(0,1).toUpperCase()+e.substr(1).toLowerCase();
  });
  }
  

• Multiplication table

  multiplicationTable = function(size) {
  var arr = [];
  for(var i=0;i1);
  }
  return arr.map(function(e){
    var r = [];
    for(var j =1;j1;j++){
      r.push(e*j);
    }
    return r;
  });
  }
  

• Basic JS - Building a calculator

  var Calculator = {};
  Calculator.add = function(a,b){return a+b}
  Calculator.subtract = function(a,b){return a-b}
  Calculator.multiply = function(a,b){return a*b}
  Calculator.divide = function(a,b){return b?a/b:false}
  

• Milk and Cookies for Santa

  function timeForMilkAndCookies(date){
  return date.getMonth()==11&&date.getDate()==24;
  }
  

• Cylon Evolution

  function Cylon(model){
  this.model = model;
  this.attack = function(){
    return 'Destroy all humans!';
  };
  }
  function HumanSkin(model){
  this.model = model;
  this.attack = function(){
    return 'Destroy all humans!';
  };
  this.infiltrate = function(){
    return 'Infiltrate the colonies';
  };
  }
  HumanSkin.prototype = new Cylon();
  

• Javascript filter - 2

  function roomMates( rooms, floor ){
  return rooms.filter(function(e,i){return e&&Math.floor(i/6)==floor-1});
  }
  

• Array Helpers

  Array.prototype.square = function(){
  return this.map(function(e){return e*e});
  }
  Array.prototype.cube = function(){
  return this.map(function(e){return e*e*e});
  }
  Array.prototype.sum = function(){
  return this.length?this.reduce(function(e,b){return e+b}):0;
  }
  Array.prototype.average = function(){
  return this.sum()/this.length;
  }
  Array.prototype.even = function(){
  return this.filter(function(e){return e%2==0});
  }
  Array.prototype.odd = function(){
  return this.filter(function(e){return e%2});
  }
  

• Simple elevator

  function goto(level,button){
  if(typeof level != 'number'|| level<0||level>3||!/[0-3]/.test(button))return 0;
  return parseInt(button)-level;
  }
  

• Use reduce() to calculate the sum of the values in an array

  function sum(array) {
  return array.reduce(function(a,b){return a+b});
  }
  

• Return the Missing Element

  function getMissingElement(superImportantArray){
  return 45-superImportantArray.reduce(function(a, b){
    return a+b;
  });
  }
  

• The reject() function

  function reject(array, iterator) {
  return array.filter(function(e){return !iterator(e)})
  }
  

• Say "Hello World" JS Style

  var say = function(string1) {
  return function(string2){
    return string1 + ' '+string2;
  }
  }