前端开发方法集

日期格式化

// 格式化日期类型,fmt格式可选择
function dateFormat(fmt, date) {
  let ret;
  let opt = {
    "Y+": date.getFullYear().toString(), // 年
    "M+": (date.getMonth() + 1).toString(), // 月
    "D+": date.getDate().toString(), // 日
    "h+": date.getHours().toString(), // 时
    "m+": date.getMinutes().toString(), // 分
    "s+": date.getSeconds().toString(), // 秒
    "ms+": date.getMilliseconds().toString() // 毫秒
  };
  for (let k in opt) {
    ret = new RegExp("(" + k + ")").exec(fmt);
    if (ret) {
      fmt = fmt.replace(ret[1], ret[1].length == 1 ? opt[k] : opt[k].padStart(ret[1].length, "0"));
    }
  }
  return fmt;
}
// 格式化当前时间
dateFormat("YYYY-MM-DD hh:mm:ss.ms", new Date());
// 格式化特定时间
let date = new Date();
let fDate = dateFormat("YYYY-MM-DD hh:mm:ss.ms", new Date(date));

时间转换（秒数转时分秒）

function timeFormat (sec) {
    let minite = Math.floor((sec / 60 % 60)) < 10 ? '0' + Math.floor((sec / 60 % 60)) : Math.floor((sec / 60 % 60));
    let second = Math.floor((sec % 60)) < 10 ? '0' + Math.floor((sec % 60)) : Math.floor((sec % 60));
    if (sec < 3600) {
        return `${minite}:${second}`;
    } else {
        let hour = Math.floor(sec / 3600) < 10 ? '0' + Math.floor(sec / 3600) : Math.floor(sec / 3600);
        return `${hour}:${minite}:${second}`;
    }
}

计算时分秒差值

// 计算时分秒差值
function timeDiffer(beginTime, endTime) {
  let ret = {};
  let date = new Date();
  let sTime = Date.parse(dateFormat("YYYY/MM/DD", date) + " " + beginTime);
  if (beginTime >= endTime) {
    date.setDate(date.getDate() + 1);
  }
  let eTime = Date.parse(dateFormat("YYYY/MM/DD", date) + " " + endTime);
  let differ = eTime - sTime;
  let hour = Math.floor(differ / 1000 / 60 / 60);
  let minute = Math.floor(differ / 1000 / 60 - hour * 60);
  let second = Math.floor(differ / 1000 - hour * 60 * 60);
  ret = {
    differHour: hour,
    differMinute: minute,
    differSecond: second
  };
  return ret;
}
let { differHour, differMinute, differSecond } = timeDiffer(beginTime, endTime);

(数组/对象)(深/浅)拷贝

let list = [{ name: "o" }];
let obj = { stu: { name: "o" } };

// 数组浅拷贝
let listCopy1 = [].concat(list);
let listCopy2 = list.slice();
let listCopy3 = Array.from(list);
let listCopy4 = [...list];

// 对象浅拷贝
let objCopy1 = Object.assign({}, obj);
let objCopy2 = { ...obj };

// 数组|对象深拷贝
let listCopy = JSON.parse(JSON.stringify(list));
let objCopy = JSON.parse(JSON.stringify(obj));

// 深拷贝，即复制并独立一份数据，操作不影响原数据
function deepCopy(obj) {
  if (typeof obj !== "object") {
    return obj;
  }
  let result = Array.isArray(obj) ? [] : {};
  for (let i in obj) {
    if (obj.hasOwnProperty(i)) {
      if (typeof obj[i] === "object" && obj[i] !== null) {
        result[i] = deepCopy(obj[i]);
      } else {
        result[i] = obj[i];
      }
    }
  }
  return result;
}

// 深拷贝
function deepClone(obj) {
  let copyObj = null;
  if (typeof obj === "object" && obj !== null) {
    copyObj = Array.isArray(obj) ? [] : {};
    for (let i in obj) {
      copyObj[i] = deepClone(obj[i]);
    }
  } else {
    copyObj = obj;
  }
  return copyObj;
}

数组去重

// ES6最简方法
let result = [];
if (Array.isArray(arr)) {
  result = new Set(arr);
}
function unique(arr) {
  return Array.from(new Set(arr));
}

// filter去重
function unique(arr) {
  return arr.filter((item, index, arr) => {
    // 当前元素在原数据中的第一个索引等于当前索引值，否则返回当前元素
    return arr.indexOf(item, 0) == index;
  });
}

// 数组去重
function unique(arr) {
  if (!Array.isArray(arr)) {
    return;
  }
  let result = [];
  for (let i = 0; i < arr.length; i++) {
    if (result.indexOf(arr[i]) === -1) {
      result.push(arr[i]);
    }
  }
  return result;
}
function unique(arr) {
  if (Array.isArray(arr)) {
    let result = [];
    for (let i = 0, len = arr.length; i < len; i++) {
      if (!result.includes(arr[i])) {
        result.push(arr[i]);
      }
    }
    return result;
  }
}

数组对象排序

// 数组对象排序，比较两个字符串
list.sort((a, b) => {
  return a.id.localeCompare(b.id);
});

获取上/下个月日期

// 下个月
let date = new Date(this.startDate);
let nextMonthDate = date.setMonth(date.getMonth() + 1);
this.endDate = dateFormat("YYYY-MM-DD", new Date(nextMonthDate));

// 上个月
let lastMonthDate = date.setMonth(date.getMonth() - 1);

获取前/后7天日期

// 前7天
let date = new Date(this.startDate);
let afterDate = date.setDate(date.getDate() + 6);
this.endDate = dateFormat("YYYY-MM-DD", new Date(afterDate));

// 后7天
let afterDate = date.setDate(date.getDate() - 6);

一周日期

let weeks=["周一","周二","周三","周四","周五","周六","周日"];
for (let i = 0; i<7; i++){
  let date = new Date();
  let index = date.getDay() ? date.getDay() - 1 : 6;
  let nowDate = date.setDate(date.getDate() - index + i);
  let formatDate = dateFormat("MM-DD", new Date(nowDate));
  let week = weeks[i]; 
  let weekDate = `${formatDate}(${week})`;
  this.weekDateColumns.push(weekDate);
}

点击内容切换

let len = this.assistList.length - 1;
if (this.index < len) {
  this.index++;
  this.assistInfo = this.assistList[this.index];
} else {
  this.index = 0;
  this.assistInfo = this.assistList[this.index];
}

时分秒

时：`parseInt(count/60/60)`
分：`parseInt(count/60)%60`
秒：`parseInt(count%60)`

数组对象，拼接字符串

let arr = [
    { id: 1, name: "Andy" },
    { id: 2, name: "Jim" },
    { id: 3, name: "Lucy" },
    { id: 4, name: "Cherry" },
];
let str = arr.map((item) => {
    return item.name;
}).join(",");

当月第一天和最后一天

// 第一天
let date = new Date();
date.setDate(1);
console.log(dateFormat("YYYY-MM-DD", date));

// 最后一天
let date = new Date();
let lastDay = new Date(date.getFullYear(), date.getMonth() + 1, 0);
console.log(dateFormat("YYYY-MM-DD", lastDay));

fetch接口请求

let api = "https://api.com";
let headerConfig = {
  headers: {
    Accept: "application/json",
  },
};
async function request() {
  let res = await fetch(api, headerConfig);
  let data = await res.json();
}

按键处理方法

window.addEventListener("keydown", (e) => {
  let container = document.querySelector("#container");
  let { key, keyCode, code } = e;
  let template = "";
  [
    {
      title: "e.key",
      content: key == " " ? "Space" : key,
    },
    {
      title: "e.keyCode",
      content: keyCode,
    },
    {
      title: "e.code",
      content: code,
    },
  ].forEach((item) => {
    template += `
${item.title}${item.content}
`;
  });
  container.innerHTML = template;
});

返回顶部

html,
body {
  scroll-behavior: smooth;
}
.back {
  position: sticky;
  float: right;
  top: -110px;
  margin-top: -50px;
  border-radius: 50%;
  background: url("") center no-repeat dodgerblue;
  background-size: 50%;
  width: 50px;
  height: 50px;
  transform: translateY(calc(100vh + 50px));
}

自适应内部元素

figure {
  max-width: 300px;
  max-width: min-content;
  margin: auto;
}
figure > img {
  max-width: inherit;
}

iview封装菜单menu

图片懒加载

const images = document.querySelectorAll("img");
const callback = (entries) => {
  entries.forEach((entry) => {
    if (entry.isIntersecting) {
      const image = entry.target;
      const data_src = image.getAttribute("data-src");
      image.setAttribute("src", data_src);
      ResizeObserver.unobserver(image);
    }
  });
};
const observer = new IntersectionObserver(callback);
images.forEach((image) => {
  observer.observe(image);
});

CSS多行文本省略

p {
  overflow: hidden;
  display: -webkit-box;
  -webkit-box-orient: vertical;
  -webkit-line-clamp: 4;
}

Vue字符串换行

1. 添加`white-space:pre`
2. 使用`
`标签替换
封装iView无限层级菜单
// 子组件



// 父组件



上传文件

  上传文件
  

.upload {
  width: 100px;
  height: 100px;
  position: relative;
}
.btn {
  width: 100%;
  height: 100%;
  box-sizing: border-box;
  border: 1px dashed rgb(31, 154, 158);
  background: #fff;
  cursor: pointer;
}
.input {
  width: 100%;
  height: 100%;
  box-sizing: border-box;
  position: absolute;
  left: 0;
  top: 0;
  opacity: 0;
}
CSS控制禁止点击
pointer-events: none; //（禁止鼠标点击事件）
单行居中，多行顶部对齐
.table-item {
    height: 100%;
    box-sizing: border-box;
    display: flex;
    flex: 1;
    flex-wrap: wrap;
    align-items: center;
    justify-content: center;
    font-size: 16upx;
    text-align: justify;
    font-weight: 600;
    span {
      width: 125upx;
      height: 65upx;
      overflow: auto;
      display: flex;
      align-items: center;
      justify-content: center;
      display: -webkit-box;
      -webkit-box-orient: vertical;
    }
  }