简单实用的18个JS代码技巧

记录一些简单实用的JS代码技巧

1.获取数据类型

封装一个公共函数来获取变量的数据类型

const getType = (value) => {
  const match = Object.prototype.toString.call(value).match(/ (\w+)]/)
  return match[1].toLocaleLowerCase()
}

getType() // undefined
getType({}}) // object
getType([]) // array
getType(1) // number
getType('fatfish') // string
getType(true) // boolean
getType(/fatfish/) // regexp

2.阻止冒泡事件

适用于所有平台的阻止冒泡事件的公共方法

const stopPropagation = (event) => {
  event = event || window.event;
  if (event.stopPropagation) {
    event.stopPropagation();
  } else {
    event.cancelBubble = true;
  }
};

3.深拷贝对象

深度复制多层嵌套的对象

//第一种
const deepClone=(obj)=>{
 var objClone = Array.isArray(obj) ? [] : {}
  if (obj && typeof obj === "object") {
    for (var key in obj) {
      // eslint-disable-next-line no-prototype-builtins
      if (obj.hasOwnProperty(key)) {
        if (obj[key] && typeof obj[key] === "object") {
          objClone[key] = deepClone(obj[key])
        } else {
          objClone[key] = obj[key]
        }
      }
    }
  }
  return objClone
}

//第一种
const deepCopy = (obj, hash = new WeakMap()) => {
  if (obj instanceof Date) {
    return new Date(obj);
  }
  if (obj instanceof RegExp) {
    return new RegExp(obj);
  }
  if (hash.has(obj)) {
    return hash.get(obj);
  }
  let allDesc = Object.getOwnPropertyDescriptors(obj);
  let cloneObj = Object.create(Object.getPrototypeOf(obj), allDesc);
  hash.set(obj, cloneObj);
  for (let key of Reflect.ownKeys(obj)) {
    if (obj[key] && typeof obj[key] === "object") {
      cloneObj[key] = deepCopy(obj[key], hash);
    } else {
      cloneObj[key] = obj[key];
    }
  }
  return cloneObj;
};

4.设置cookie值

封装公共的设置cookie值，提高开发效率

const setCookie = (key, value, expire) => {
  const d = new Date();
  d.setDate(d.getDate() + expire);
  document.cookie = `${key}=${value};expires=${d.toUTCString()}`;
};

5.获取cookie值

除了设置cookie值外，我们还需要获取cookie值

const getCookie = (key) => {
  const cookieStr = unescape(document.cookie);
  const arr = cookieStr.split("; ");
  let cookieValue = "";
  for (let i = 0; i < arr.length; i++) {
    const temp = arr[i].split("=");
    if (temp[0] === key) {
      cookieValue = temp[1];
      break;
    }
  }
  return cookieValue;
};

6.删除cookie

删除cookie其实就是给cookie设置过期时间，超过这个时刻它就会立即过期

const delCookie = (key) => {
  document.cookie = `${encodeURIComponent(key)}=;expires=${new Date()}`;
};

7.生成随机字符串

const randomString = (len) => {
  let chars = "ABCDEFGHJKMNPQRSTWXYZabcdefhijkmnprstwxyz123456789";
  let strLen = chars.length;
  let randomStr = "";
  for (let i = 0; i < len; i++) {
    randomStr += chars.charAt(Math.floor(Math.random() * strLen));
  }
  return randomStr;
};

randomString(10) // pfkMfjEJ6x
randomString(20) // ce6tEx1km4idRNMtym2S

8.从数组中获取一个随机值

类似抽奖，出现一个随机结果

const getRandomValue = array => array[Math.floor(Math.random() * array.length)]; 
const prizes = [  '$100', '', ''，'1234' ]

getRandomValue(prizes) // 
getRandomValue(prizes) // 
getRandomValue(prizes) // 

9.随机生成指定范围内的数值

const randomNum = (min, max) => Math.floor(Math.random() * (max - min + 1)) + min;
randomNum(1, 10) // 6
randomNum(10, 20) // 11

10.将字符串的首字母变成大写

const fistLetterUpper = (str) => {
  return str.charAt(0).toUpperCase() + str.slice(1);
};

fistLetterUpper('fish') // Fish

11.一键滚动到页面顶部

const scrollToTop = () => {
  window.scrollTo({ top: 0, left: 0, behavior: "smooth" });
};

12.一键滚动到页面底部

const scrollToBottom = () => {
  window.scrollTo({
    top: document.documentElement.offsetHeight,
    left: 0,
    behavior: "smooth",
  });
};

13.将元素滚动到可见区域

使用 scrollIntoView 就可以实现将元素滚动到可见区域

const smoothScroll = (element) => {
  element.scrollIntoView({
    behavior: "smooth",
  });
};

14.全屏显示

const goToFullScreen = (element) => {
  element = element || document.body;
  if (element.requestFullscreen) {
    element.requestFullscreen();
  } else if (element.mozRequestFullScreen) {
    element.mozRequestFullScreen();
  } else if (element.msRequestFullscreen) {
    element.msRequestFullscreen();
  } else if (element.webkitRequestFullscreen) {
    element.webkitRequestFullScreen();
  }
};

15.退出全屏显示

const goExitFullscreen = () => {
  if (document.exitFullscreen) {
    document.exitFullscreen();
  } else if (document.msExitFullscreen) {
    document.msExitFullscreen();
  } else if (document.mozCancelFullScreen) {
    document.mozCancelFullScreen();
  } else if (document.webkitExitFullscreen) {
    document.webkitExitFullscreen();
  }
};

16.判断设备类型

有时候经常会遇到一些在手机端显示逻辑A，在pc端显示逻辑B

const isMobile = () => {
  return !!navigator.userAgent.match(
    /(iPhone|iPod|Android|ios|iOS|iPad|Backerry|WebOS|Symbian|Windows Phone|Phone)/i
  );
};

17.判断设备是Android还是IOS

记得有写过一个H5下载页面，安卓和ios分别对应不同的下载包

const isAndroid = () => {
  return /android/i.test(navigator.userAgent.toLowerCase());
};

const isIOS = () => {
  let reg = /iPhone|iPad|iPod|iOS|Macintosh/i;
  return reg.test(navigator.userAgent.toLowerCase());
};

18.货比格式化方法

//让人头疼的正则表达式
const formatMoney = (money) => {
  return money.replace(new RegExp(`(?!^)(?=(\\d{3})+${money.includes('.') ? '\\.' : '$'})`, 'g'), ',')  
}

formatMoney('123456789') // '123,456,789'
formatMoney('123456789.123') // '123,456,789.123'
formatMoney('123') // '123'

//另外一种简单的方法
const formatMoney = (money) => {
  return money.toLocaleString()
}

formatMoney(123456789) // '123,456,789'
formatMoney(123456789.123) // '123,456,789.123'
formatMoney(123) // '123'