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文章目录

• 数组去重

  • 方式一

    // 使用Set去重并转为数组  var fruits1 = ['banana', 'apple', 'orange', 'watermelon', 'apple', 'orange', 'grape', 'apple'];  var uniqueFruits1 = Array.from(new Set(fruits1));  console.log(uniqueFruits1);  // ["banana", "apple", "orange", "watermelon", "grape"]

  • 方式二

    // 使用Spread运算  var uniqueFruits2 = [...new Set(fruits1)];  console.log(uniqueFruits2);  // ["banana", "apple", "orange", "watermelon", "grape"]

  • 方式三

    // 使用forEach遍历并添加  var uniqueFruits3 = [];  fruits1.forEach(element => {    if(uniqueFruits3.indexOf(element) === -1) {      uniqueFruits3.push(element);    }  });  console.log(uniqueFruits3);  // ["banana", "apple", "orange", "watermelon", "grape"]

  • 方式四

    // 使用includes方法  var uniqueFruits4 = [];  fruits1.forEach((element) => {    if(!uniqueFruits4.includes(element)){      uniqueFruits4.push(element);    }  });  console.log(uniqueFruits4);  // ["banana", "apple", "orange", "watermelon", "grape"]

• 数组扁平化

  • 方法一

    // 利用concat方法递归扁平化  function flatten(arr) {    while (arr.some((item) => Array.isArray(item))) {      arr = [].concat(...arr);    }    return arr;  }  const newArr = flatten([1, 2, 3, [4, 5, 6, [7, 8, 9]]]);  console.log(newArr);  // [1, 2, 3, 4, 5, 6, 7, 8, 9]

• 将一维数组分割为二维

  • 代码示例

    // 定义分割函数  function changeArrGroup (arr, newArrLength) {    let changeIndex = 0;    let secondArr = [];    while (changeIndex < arr.length) {      secondArr.push(arr.slice(changeIndex, changeIndex += newArrLength));    }    return secondArr;  }  console.log(changeArrGroup([1,2,3,4,5,6,7,8,9],3));  // [[1, 2, 3], [4, 5, 6], [7, 8, 9]]

• 移动0到末尾

  • 代码示例

    // 移动0到尾部  function removeZero(nums){    let num = nums.toString().split('');    let n = 0;    for(let i = 0; i < num.length; i++){      if(num[i] != '0'){        num[n] = num[i];        n++;      }    }    for(let k = n; k < num.length; k++){      num[k] = '0';    }    return Number(num.join(''));  }  console.log(removeZero(102000003040500000006n));  // 1234560000

• 替换特定的值

  • 代码示例

    // 替换数组开头的两个元素  var fruits2 = ['banana', 'apple', 'orange', 'watermelon', 'apple', 'orange', 'grape', 'apple'];  fruits2.splice(0, 2, 'pitaya', 'mango');  console.log(fruits2);  // ["pitaya", "mango", "orange", "watermelon", "apple", "orange", "grape", "apple"]

• 从对象映射出数组（map与Array.from）

  • 代码示例一

    // 使用map方法  var friends1 = [    {name: 'John', age: 22},    {name: 'Peter', age: 23},    {name: 'Mark', age: 24},    {name: 'Maria', age: 25},    {name: 'Monica', age: 26},    {name: 'Martha', age: 27}  ];  var friendName1 = friends1.map((item) => {    return item.name;  });  console.log(friendName1);  // ["John", "Peter", "Mark", "Maria", "Monica", "Martha"]

  • 代码示例二

    // 使用Array.from和对象展开  var friendName2 = Array.from(friends1, ({name}) => name);  console.log(friendName2);  // ["John", "Peter", "Mark", "Maria", "Monica", "Martha"]

• 转成空数组

  • 代码示例

    // 通过设置长度为0  var fruits3 = ['banana', 'apple', 'orange', 'watermelon', 'apple', 'orange', 'grape', 'apple'];  fruits3.length = 0;  console.log(fruits3);  // []

• 数组转化为对象

  • 代码示例

    // 使用对象展开操作符  var fruits4 = ['banana', 'apple', 'orange', 'watermelon', 'apple', 'orange', 'grape', 'apple'];  var fruits4Obj = {    ...fruits4  };  console.log(fruits4Obj);  // {0: "banana", 1: "apple", 2: "orange", 3: "watermelon", 4: "apple", 5: "orange", 6: "grape", 7: "apple"}

• 填充数组

  • 代码示例

    // 创建长度为10的数组，全部填充'520'  var newArray = new Array(10).fill('520');  console.log(newArray);  // ["520", "520", "520", "520", "520", "520", "520", "520", "520", "520"]

• 合并数组

  • 代码示例一

    // 使用concat方法  var fruit5 = ['banana', 'apple', 'orange', 'watermelon', 'grape'];  var meat = ['poultry', 'beef', 'fish'];  var vegetable = ['potato', 'tomato', 'cucumber'];  var concat1 = fruit5.concat(meat);  console.log(concat1);  // ["banana", "apple", "orange", "watermelon", "grape", "poultry", "beef", "fish"]

  • 代码示例二

    // 使用spread运算合并多个数组  var food = [...fruit5, ...meat, ...vegetable];  console.log(food);  // ["banana", "apple", "orange", "watermelon", "grape", "poultry", "beef", "fish", "potato", "tomato", "cucumber"]

• 求数组交集

  • 代码示例

    // 找出两个数组的交集  var numOne = [0,1,2,4,6,8,8];  var numTwo = [1,2,3,8,8];  var duplicatedValues = [...new Set(numOne)].filter(item => numTwo.includes(item));  console.log(duplicatedValues);  // [1, 2, 8]

• 用过滤从数组中删除假值，保留真值

  • 代码示例

    // 过滤数组中的假值  var mixedArr = [0, NaN, 9, false, undefined, '', 'black'];  var trueArr = mixedArr.filter(Boolean);  console.log(trueArr);  // [9, "black"]

• 从数组中获取随机值

  • 代码示例

    // 随机获取数组中的一个元素  var fruit6 = ['banana', 'apple', 'orange', 'watermelon', 'grape'];  var fruit6random = fruit6[Math.floor(Math.random() * (fruit6.length))];  console.log(fruit6random);  // "grape" 或者数组中的其他项

• 获取月份天数

  • 代码示例

    // 获取指定年月的天数  function getMonthCountDay (year, month){    return 32 - new Date(year, month-1, 32).getDate();  }

• 数据类型判断

  • 代码示例

    // 判断数据类型  function typeOf(obj) {    const o = Object.prototype.toString.call(obj);    return (      o.match(/\s+(\w+)/)[1]      .slice(0, 1)      .toLocaleLowerCase() +      o.match(/\s+(\w+)/)[1].slice(1)    );  }  console.log(typeOf(123));

• 通过JSON.stringify做对象筛选

  • 代码示例

    // 定义替换函数  const replaceFun = (key, value) => {    console.log(key, value);    if (key === 'name') {      return undefined;    }    return value;  };  const myIntro = {    name: 'han',    age: 18,    link: 'FE',  };  console.log(JSON.stringify(myIntro, replaceFun));  // {"age":18,"link":"FE"}

• 对象里的值相加

  • 代码示例

    // 遍历对象并累加  let obj = [    {a: 1, b: 2},    {a: 3, b: 4},    {c: 5, b: 2},    {c: 1, d: 4, f: 6}  ];  let newObj = {};  for(let item of obj){    for(let i in item){      if(!newObj.hasOwnProperty(i)){        newObj[i] = item[i];      } else{        newObj[i] += item[i];      }    }  }  console.log(newObj);  // {a:4, b:8, c:6, d:4}

• 利用reduce将数组转为对象，且将其value拼接为新对象

  • 代码示例

    // 将数组转为对象并拼接value  let user = [    {name: '张三', age: 26},    {name: '赵四', age: 27},    {name: '李五', age: 28},    {name: '王六', age: 29},    {name: '周七', age: 30},    {name: '李八', age: 31}  ];  let o = user.reduce((obj, item) => {    return {      ...obj,      [item.name]: item.age    };  }, {});  console.log(o);  // {张三:26, 赵四:27, 李五:28, 王六:29, 周七:30, 李八:31}

• 通过递归的方式返回父级节点

  • 代码示例

    // 递归删除父级节点及其子节点  let obj = [    {      name: '小王',      age: 65,      nodeKey: '1',      children: [        {          name: '小李',          age: 30,          nodeKey: '1-1',          children: [            {              name: '小胡',              age: 6,              nodeKey: '1-1-1'            }          ]        },        {          name: '小白',          age: 13,          nodeKey: '1-2'        }      ]    }  ];  const node = {    name: '小胡',    age: 6,    nodeKey: '1-1-1'  };  const getNode = (arr, node) => {    for (let i = 0; i < arr.length; i++) {      const currentNode = arr[i];      if (currentNode.nodeKey === node.nodeKey) {        if (!currentNode.parent) {          return currentNode;        } else {          return true;        }      } else {        if (currentNode.children && currentNode.children.length > 0) {          currentNode.children.map((o) => {            o.parent = currentNode;          });          if (getNode(currentNode.children, node)) {            return currentNode;          }        }      }    }  };  console.log(getNode(obj, node));

• 10000个数取最大的10个

  • 代码示例

    // 生成10000个随机数并提取最大的10个  let arr = [];  for(let i=0; i < 10000; i++){    arr.push(Math.floor(Math.random()*10000));  }  console.log(arr);  // 去重  arr = Array.from(new Set(arr));  console.log(arr);  // 排序  arr = arr.sort(function(a,b){    return b-a;  });  console.log(arr);  // 取前10个数  max10Arr = arr.slice(0,10);  console.log(max10Arr);

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