常用方法封装

常用方法封装

修改对象的key值

//如果data是对象可以免去遍历这一步
replaceKey(data, oldKeyName, newKeyName) {
      data.forEach(item => {
        for (let key in item) {
          if (key == oldKeyName) {
            item[newKeyName] = item[key];
            delete item[key];
          }
        }
      });
      return data;
    }

es6解构赋值删除不需要的属性

let {phone, qqList, ...obj} = {ck1: '1', phone:"10086", qqList:{}, ck2: '2', ck3: '3'};
console.log(obj); // {ck1: '1', ck2: '2', ck3: '3'}

reduce删除对象中重复的属性–网上的例子

let person = [
     {id: 0, name: "小明"},
     {id: 1, name: "小张"},
     {id: 2, name: "小李"},
     {id: 3, name: "小孙"},
     {id: 1, name: "小周"},
     {id: 2, name: "小陈"},   
];

let obj = {};

person = person.reduce((cur,next) => {
    obj[next.id] ? "" : obj[next.id] = true && cur.push(next);
    return cur;
},[]) //设置cur默认类型为数组，并且初始值为空的数组
//console.log(person);

reduce数组合并去重并修改数组中对象的属性值

let arr = [{ name: '应继武', vendor: 1 }, { name: '李四', vendor: 1 },{ name: '张三', vendor: 1 }];
let arr1 = [{ name: '应继武', vendor: 2 }, { name: '张三', vendor: 2 }, { name: '王五', vendor: 2 }];
let list = [...arr, ...arr1];

let d = []
let hash = {}
d = list.reduce((item, next, index, sArr) => {
    // console.log(item, next, index, sArr)
    hash[next.name] ? item=setArr(next.name,item) : hash[next.name] = true && item.push(next)
    return item
}, [])

function setArr(name,list){
    list.forEach(item=>{
        if(item.name===name){
            item.vendor=3
        }
    })
    return list
}
//console.log(d)
//[{ name: '应继武', vendor: 3 }, { name: '李四', vendor: 1 },{ name: '张三', vendor: 3 }, { name: '王五', vendor: 2 }]

检测是否是数组

Array.isArray([]);  // true
Array.isArray(undefined); // false;

array instanceof Array; // true 检测对象的原型链是否指向构造函数的prototype对象

数组的一些操作

//遍历数组
let arr=[1,2,3,4,3,2,1];
//forEach遍历数组的话，不能用break跳出循环，也不能用return返回外层。
//for in遍历的是数组的索引（即键名），而for of遍历的是数组元素值
for (let value of arr) {//break 跳出循环下面的方法继续执行；return 终止运行
  console.log(value);//输出1,2,3,4,3,2,1
}

//map 返回一个新数组
let users = [
  {name: "张含韵", "email": "zhang@email.com"},
  {name: "江一燕",   "email": "jiang@email.com"},
  {name: "李小璐",  "email": "li@email.com"}
];
let emails = users.map(item=>item.email);

//filter 返回过滤后的新数组
let arr=[1,2,3,4,3,2,1,2];
let newArr1=arr.filter((value,index,arr)=>value>=3)
console.log(newArr1);//输出[3,4,3]

时间戳转 y-m-d h:m:s

function timestampToTime(timestamp,full) {
    var date = timestamp.length == 10 ? new Date(timestamp * 1000) : new Date(timestamp);//时间戳为10位需*1000，时间戳为13位的话不需乘1000
    Y = date.getFullYear() + '-';
    M = (date.getMonth() + 1 < 10 ? '0' + (date.getMonth() + 1) : date.getMonth() + 1) + '-';
    D = date.getDate() + ' ';
    h = date.getHours() + ':';
    m = date.getMinutes() + ':';
    s = date.getSeconds();
    //return Y+M+D+h+m+s;
    if (full) {
        return Y + M + D + h + m + s;//2018-11-11 11:11:11
    } else {
        return { ymd: Y + M + D, hms: h + m + s }
    }
}

判断一个变量是不是空对象

function isEmptyObj(obj) {
    return obj !== null && typeof obj === 'object' && !Array.isArray(obj) && (Object.getOwnPropertyNames(obj).length === 0) && (Object.getOwnPropertySymbols(obj).length === 0)
}

分割一位数组

function cutArr(size, arr) {
    var result = [];
    for (var i = 0; i < arr.length; i += size) {
        result.push(data.slice(i, i + size));
    }
    return result
}
//示例
var data = [
  {name:'Liming',age:'25'},
  {name:'Liming',age:'25'},
  {name:'Liming',age:'25'},
  {name:'Liming',age:'25'},
  {name:'Liming',age:'25'},
  {name:'Liming',age:'25'},
  {name:'Liming',age:'25'},
  {name:'Liming',age:'25'},
  {name:'Liming',age:'25'},
  {name:'Liming',age:'25'},
];
cutArr(3,data)

jq判断div是否滚动到底部（loadMore）

$('#div').scroll(function (event) {
  var scrollTop = $(this).scrollTop();//表示滚动条滚动的高度
  var height = $(this).height();//div高度
  var scrollHeight = $(this)[0].scrollHeight;//表示滚动条需要滚动的高度
  // var scrollTop = event.currentTarget.scrollTop;
  // var height = event.currentTarget.clientHeight;
  // var scrollHeight = event.currentTarget.scrollHeight;
  //console.log(scrollTop, height, scrollHeight);
  if (scrollTop + height == scrollHeight) {
    console.log('到底了');
  }
  if (scrollTop == 0) {
    console.log('到顶了');
  }
})