freeCodeCamp 基础算法

将摄氏度转换为华氏度

function convertToF(celsius) {
  let fahrenheit = celsius * 9/5 +32;
  return fahrenheit;
}

convertToF(30);

反转字符串

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

reverseString("hello");

计算整数的阶乘

function factorialize(num) {
  let res = 1;
  while(num > 0) {
    res *= num;
    num--
  }
  return res;
}

factorialize(5);

找出字符串中的最长单词

function findLongestWordLength(str) {
  const arr1 = str.split(/[^a-zA-Z]/);
  const filt = arr1.reduce((prev, next) => {
    return next.length > prev ? next.length : prev;
  }, 0)
  return filt;
}

findLongestWordLength("The quick brown fox jumped over the lazy dog");

找出多个数组中的最大数字

function largestOfFour(arr) {
  let res = 0;
  res = arr.map(item => {
     return item.reduce((prev, next) => {
      return Math.max(prev, next);
    })
  })
  console.log(res)
  return res;
}

largestOfFour([[17, 23, 25, 12], [25, 7, 34, 48], [4, -10, 18, 21], [-72, -3, -17, -10]]);

确认结尾

function confirmEnding(str, target) {
  const reg = new RegExp(target + '$')
  return reg.test(str);
}

confirmEnding("Bastian", "n");

重复输出字符串

function repeatStringNumTimes(str, num) {
  if (num < 1) return ''
  let res = ''
  while (num > 0) {
    res += str;
    num--;
  }
  return res;
}

repeatStringNumTimes("abc", 3);

截断字符串

function truncateString(str, num) {
  if (num < str.length) {
    return str.slice(0, num) + '...';
  }
  return str
}

truncateString("A-tisket a-tasket A green and yellow basket", 8);

按参数过滤数组

function findElement(arr, func) {
  let num = arr.filter(item => {
    return func(item);
  });
  return num[0];
}

findElement([1, 2, 3, 4], num => num % 2 === 0);

基本类型布尔值的检查

function booWho(bool) {
  return typeof bool === 'boolean';
}

booWho(null);

句中单词首字母大写

function titleCase(str) {
  const arr = str.toLowerCase().split(/\s+/g);
  const arr1 = arr.map(item => {
    return item.charAt(0).toUpperCase() + item.slice(1) 
  });

  return arr1.join(' ');
}

titleCase("I'm a little tea pot");

Slice 与 Splice

function frankenSplice(arr1, arr2, n) {
  return arr2.slice(0, n).concat(arr1).concat(arr2.slice(n));
}

frankenSplice([1, 2, 3], [4, 5, 6], 1);

过滤数组中的假值

function bouncer(arr) {
  return arr.filter(item => {
    return item
  });
}

bouncer([7, "ate", "", false, 9]);

找出元素在排序后数组中的索引

function getIndexToIns(arr, num) {
  const arr1 = arr.sort((a,b) => {
    return a - b; 
  });
  for(let i = 0; i < arr1.length; i++) {
    if (arr1[i] >= num) {
      return i;
    }
  }
  return arr1.length;
}

getIndexToIns([40, 60], 50);

比较字符串

function mutation([str1, str2]) {
  const arr = str2.toLowerCase().split('');
  return arr.every(item => {
    return str1.toLowerCase().includes(item)
  })
}

mutation(["hello", "hey"]);

分割数组

function chunkArrayInGroups(arr, size) {
  const res = []
  let num = arr.length;
  let index= 0;
  while(index < num) {
    res.push(arr.slice(index, index + size))
    index += size;
  }
  return res;
}

chunkArrayInGroups(["a", "b", "c", "d"], 2);