标签 javascript 下的文章

// 添加一个适当的事件监听器
obj.addEventListener("cat", function(e) { process(e.detail) })

// 创建并分发事件
var event = new CustomEvent("cat", {"detail":{"hazcheeseburger":true}})
obj.dispatchEvent(event)

var raw = function (args) {
  var keys = Object.keys(args);
  keys = keys.sort()
  var newArgs = {};
  keys.forEach(function (key) {
    newArgs[key.toLowerCase()] = args[key];
  });

  var string = '';
  for (var k in newArgs) {
    string += '&' + k + '=' + newArgs[k];
  }
  string = string.substr(1);
  return string;
};

var createNonceStr = function () {
  return Math.random().toString(36).substr(2, 15);
};

var createTimestamp = function () {
  return parseInt(new Date().getTime() / 1000) + '';
};

class EventBus {
  constructor() {
    this._events = [];//存储自定义事件
  }

  /**
   * 注册事件和处理函数
   * @param event
   * @param fn
   */
  on(event, fn) {
    if (Array.isArray(event)) {
      for (let i = 0, l = event.length; i < l; i++) {
        this.on(event[i], fn)
      }
    } else {
      // 存在直接push, 不存在创建为空数组再push
      (this._events[event] || (this._events[event] = [])).push(fn)
    }
  }

  /**
   * 注册事件和处理函数,触发一次后销毁
   * @param event
   * @param fn
   */
  once(event, fn) {
    let _self=this;
    function handler() {
      _self.off(event, handler);
      fn.apply(null,arguments);//emit里面调用时会给on方法传参
    }

    handler.fn = fn;//off里面根据这个判断销毁事件
    this.on(event, handler);
  }

  /**
   * 销毁事件和处理函数
   * @param event
   * @param fn
   */
  off(event, fn) {
    //不传参数表示清空所有
    if (!arguments.length) {
      this._events = [];
    }
    //数组循环清空
    if (Array.isArray(event)) {
      for (let i = 0, l = event.length; i < l; i++) {
        this.off(event[i], fn)
      }
    }
    const cbs = this._events[event];
    if (!cbs) {
      return;
    }
    //不传第二参表示清空某事件所有监听函数
    if (arguments.length == 1) {
      this._events[event] = null
    }
    let cb, i = cbs.length
    while (i--) {
      cb = cbs[i]
      if (cb === fn || cb.fn === fn) { //cb.fn===fn用来移除once注册的事件
        cbs.splice(i, 1)
        break
      }
    }
  }

  /**
   * 触发某事件所有回调并带参数
   * @param event
   */
  emit(event) {
    //once删除事件会导致下面循环过程中this._events内fn前移, 所以此处复制成新数组
    let cbs = [...this._events[event]];
    if (cbs) {
      for (let i = 0, l = cbs.length; i < l; i++) {
        try {
          cbs[i].apply(null,[...arguments].slice(1))
        } catch (e) {
          new Error(e, `event handler for "${event}"`)
        }
      }
    }
  }
}
//测试用例
let eb=new EventBus();
eb.once('event1',params=>console.log(11,params));
eb.on('event1',params=>console.log(22,params));
eb.emit('event1',33)

数组 Array

数组去重

function noRepeat(arr) {
  return [...new Set(arr)];
}

查找数组最大

function arrayMax(arr) {
  return Math.max(...arr);
}

查找数组最小

function arrayMin(arr) {
  return Math.min(...arr);
}

返回已 size 为长度的数组分割的原数组

function chunk(arr, size = 1) {
  return Array.from(
    {
      length: Math.ceil(arr.length / size),
    },
    (v, i) => arr.slice(i * size, i * size + size)
  );
}

检查数组中某元素出现的次数

function countOccurrences(arr, value) {
  return arr.reduce((a, v) => (v === value ? a + 1 : a + 0), 0);
}

扁平化数组

  • 默认 depth 全部展开
function flatten(arr, depth = -1) {
  if (depth === -1) {
    return [].concat(
      ...arr.map((v) => (Array.isArray(v) ? this.flatten(v) : v))
    );
  }
  if (depth === 1) {
    return arr.reduce((a, v) => a.concat(v), []);
  }
  return arr.reduce(
    (a, v) => a.concat(Array.isArray(v) ? this.flatten(v, depth - 1) : v),
    []
  );
}

对比两个数组并且返回其中不同的元素

function diffrence(arrA, arrB) {
  return arrA.filter((v) => !arrB.includes(v));
}

返回两个数组中相同的元素

function intersection(arr1, arr2) {
  return arr2.filter((v) => arr1.includes(v));
}

从右删除 n 个元素

function dropRight(arr, n = 0) {
  return n < arr.length ? arr.slice(0, arr.length - n) : [];
}

截取第一个符合条件的元素及其以后的元素

function dropElements(arr, fn) {
  while (arr.length && !fn(arr[0])) arr = arr.slice(1);
  return arr;
}

返回数组中下标间隔 nth 的元素

function everyNth(arr, nth) {
  return arr.filter((v, i) => i % nth === nth - 1);
}

返回数组中第 n 个元素

  • 支持负数
function nthElement(arr, n = 0) {
  return (n >= 0 ? arr.slice(n, n + 1) : arr.slice(n))[0];
}

返回数组头元素

function head(arr) {
  return arr[0];
}

返回数组末尾元素

function last(arr) {
  return arr[arr.length - 1];
}

数组乱排

function shuffle(arr) {
  let array = arr;
  let index = array.length;

  while (index) {
    index -= 1;
    let randomInedx = Math.floor(Math.random() * index);
    let middleware = array[index];
    array[index] = array[randomInedx];
    array[randomInedx] = middleware;
  }

  return array;
}

浏览器对象 BOM

判读浏览器是否支持 CSS 属性

/**
 * 告知浏览器支持的指定css属性情况
 * @param {String} key - css属性,是属性的名字,不需要加前缀
 * @returns {String} - 支持的属性情况
 */
function validateCssKey(key) {
  const jsKey = toCamelCase(key); // 有些css属性是连字符号形成
  if (jsKey in document.documentElement.style) {
    return key;
  }
  let validKey = "";
  // 属性名为前缀在js中的形式,属性值是前缀在css中的形式
  // 经尝试,Webkit 也可是首字母小写 webkit
  const prefixMap = {
    Webkit: "-webkit-",
    Moz: "-moz-",
    ms: "-ms-",
    O: "-o-",
  };
  for (const jsPrefix in prefixMap) {
    const styleKey = toCamelCase(`${jsPrefix}-${jsKey}`);
    if (styleKey in document.documentElement.style) {
      validKey = prefixMap[jsPrefix] + key;
      break;
    }
  }
  return validKey;
}

/**
 * 把有连字符号的字符串转化为驼峰命名法的字符串
 */
function toCamelCase(value) {
  return value.replace(/-(\w)/g, (matched, letter) => {
    return letter.toUpperCase();
  });
}

/**
 * 检查浏览器是否支持某个css属性值(es6版)
 * @param {String} key - 检查的属性值所属的css属性名
 * @param {String} value - 要检查的css属性值(不要带前缀)
 * @returns {String} - 返回浏览器支持的属性值
 */
function valiateCssValue(key, value) {
  const prefix = ["-o-", "-ms-", "-moz-", "-webkit-", ""];
  const prefixValue = prefix.map((item) => {
    return item + value;
  });
  const element = document.createElement("div");
  const eleStyle = element.style;
  // 应用每个前缀的情况,且最后也要应用上没有前缀的情况,看最后浏览器起效的何种情况
  // 这就是最好在prefix里的最后一个元素是''
  prefixValue.forEach((item) => {
    eleStyle[key] = item;
  });
  return eleStyle[key];
}

/**
 * 检查浏览器是否支持某个css属性值
 * @param {String} key - 检查的属性值所属的css属性名
 * @param {String} value - 要检查的css属性值(不要带前缀)
 * @returns {String} - 返回浏览器支持的属性值
 */
function valiateCssValue(key, value) {
  var prefix = ["-o-", "-ms-", "-moz-", "-webkit-", ""];
  var prefixValue = [];
  for (var i = 0; i < prefix.length; i++) {
    prefixValue.push(prefix[i] + value);
  }
  var element = document.createElement("div");
  var eleStyle = element.style;
  for (var j = 0; j < prefixValue.length; j++) {
    eleStyle[key] = prefixValue[j];
  }
  return eleStyle[key];
}

function validCss(key, value) {
  const validCss = validateCssKey(key);
  if (validCss) {
    return validCss;
  }
  return valiateCssValue(key, value);
}

返回当前网页地址

function currentURL() {
  return window.location.href;
}

获取滚动条位置

function getScrollPosition(el = window) {
  return {
    x: el.pageXOffset !== undefined ? el.pageXOffset : el.scrollLeft,
    y: el.pageYOffset !== undefined ? el.pageYOffset : el.scrollTop,
  };
}

获取 url 中的参数

function getURLParameters(url) {
  return url
    .match(/([^?=&]+)(=([^&]*))/g)
    .reduce(
      (a, v) => (
        (a[v.slice(0, v.indexOf("="))] = v.slice(v.indexOf("=") + 1)), a
      ),
      {}
    );
}

页面跳转,是否记录在 history 中

function redirect(url, asLink = true) {
  asLink ? (window.location.href = url) : window.location.replace(url);
}

滚动条回到顶部动画

function scrollToTop() {
  const scrollTop =
    document.documentElement.scrollTop || document.body.scrollTop;
  if (scrollTop > 0) {
    window.requestAnimationFrame(scrollToTop);
    window.scrollTo(0, c - c / 8);
  } else {
    window.cancelAnimationFrame(scrollToTop);
  }
}

复制文本

function copy(str) {
  const el = document.createElement("textarea");
  el.value = str;
  el.setAttribute("readonly", "");
  el.style.position = "absolute";
  el.style.left = "-9999px";
  el.style.top = "-9999px";
  document.body.appendChild(el);
  const selected =
    document.getSelection().rangeCount > 0
      ? document.getSelection().getRangeAt(0)
      : false;
  el.select();
  document.execCommand("copy");
  document.body.removeChild(el);
  if (selected) {
    document.getSelection().removeAllRanges();
    document.getSelection().addRange(selected);
  }
}

检测设备类型

function detectDeviceType() {
  return /Android|webOS|iPhone|iPad|iPod|BlackBerry|IEMobile|Opera Mini/i.test(
    navigator.userAgent
  )
    ? "Mobile"
    : "Desktop";
}

Cookie

function setCookie(key, value, expiredays) {
  var exdate = new Date();
  exdate.setDate(exdate.getDate() + expiredays);
  document.cookie =
    key +
    "=" +
    escape(value) +
    (expiredays == null ? "" : ";expires=" + exdate.toGMTString());
}

function delCookie(name) {
  var exp = new Date();
  exp.setTime(exp.getTime() - 1);
  var cval = getCookie(name);
  if (cval != null) {
    document.cookie = name + "=" + cval + ";expires=" + exp.toGMTString();
  }
}

function getCookie(name) {
  var arr,
    reg = new RegExp("(^| )" + name + "=([^;]*)(;|$)");
  if ((arr = document.cookie.match(reg))) {
    return arr[2];
  } else {
    return null;
  }
}

日期 Date

时间戳转换为时间

  • 默认为当前时间转换结果
  • isMs 为时间戳是否为毫秒
function timestampToTime(timestamp = Date.parse(new Date()), isMs = true) {
  const date = new Date(timestamp * (isMs ? 1 : 1000));
  return `${date.getFullYear()}-${
    date.getMonth() + 1 < 10 ? "0" + (date.getMonth() + 1) : date.getMonth() + 1
  }-${date.getDate()} ${date.getHours()}:${date.getMinutes()}:${date.getSeconds()}`;
}

文档对象 DOM

固定滚动条

/**
 * 功能描述:一些业务场景,如弹框出现时,需要禁止页面滚动,这是兼容安卓和 iOS 禁止页面滚动的解决方案
 */

let scrollTop = 0;

function preventScroll() {
  // 存储当前滚动位置
  scrollTop = window.scrollY;

  // 将可滚动区域固定定位,可滚动区域高度为 0 后就不能滚动了
  document.body.style["overflow-y"] = "hidden";
  document.body.style.position = "fixed";
  document.body.style.width = "100%";
  document.body.style.top = -scrollTop + "px";
  // document.body.style['overscroll-behavior'] = 'none'
}

function recoverScroll() {
  document.body.style["overflow-y"] = "auto";
  document.body.style.position = "static";
  // document.querySelector('body').style['overscroll-behavior'] = 'none'

  window.scrollTo(0, scrollTop);
}

判断当前位置是否为页面底部

  • 返回值为 true/false
function bottomVisible() {
  return (
    document.documentElement.clientHeight + window.scrollY >=
    (document.documentElement.scrollHeight ||
      document.documentElement.clientHeight)
  );
}

判断元素是否在可视范围内

  • partiallyVisible 为是否为完全可见
function elementIsVisibleInViewport(el, partiallyVisible = false) {
  const { top, left, bottom, right } = el.getBoundingClientRect();

  return partiallyVisible
    ? ((top > 0 && top < innerHeight) ||
        (bottom > 0 && bottom < innerHeight)) &&
        ((left > 0 && left < innerWidth) || (right > 0 && right < innerWidth))
    : top >= 0 && left >= 0 && bottom <= innerHeight && right <= innerWidth;
}

获取元素 css 样式

function getStyle(el, ruleName) {
  return getComputedStyle(el, null).getPropertyValue(ruleName);
}

进入全屏

function launchFullscreen(element) {
  if (element.requestFullscreen) {
    element.requestFullscreen();
  } else if (element.mozRequestFullScreen) {
    element.mozRequestFullScreen();
  } else if (element.msRequestFullscreen) {
    element.msRequestFullscreen();
  } else if (element.webkitRequestFullscreen) {
    element.webkitRequestFullScreen();
  }
}

launchFullscreen(document.documentElement);
launchFullscreen(document.getElementById("id")); //某个元素进入全屏

退出全屏

function exitFullscreen() {
  if (document.exitFullscreen) {
    document.exitFullscreen();
  } else if (document.msExitFullscreen) {
    document.msExitFullscreen();
  } else if (document.mozCancelFullScreen) {
    document.mozCancelFullScreen();
  } else if (document.webkitExitFullscreen) {
    document.webkitExitFullscreen();
  }
}

exitFullscreen();

全屏事件

document.addEventListener("fullscreenchange", function (e) {
  if (document.fullscreenElement) {
    console.log("进入全屏");
  } else {
    console.log("退出全屏");
  }
});

数字 Number

数字千分位分割

function commafy(num) {
  return num.toString().indexOf(".") !== -1
    ? num.toLocaleString()
    : num.toString().replace(/(\d)(?=(?:\d{3})+$)/g, "$1,");
}

生成随机数

function randomNum(min, max) {
  switch (arguments.length) {
    case 1:
      return parseInt(Math.random() * min + 1, 10);
    case 2:
      return parseInt(Math.random() * (max - min + 1) + min, 10);
    default:
      return 0;
  }
}

摘自 https://segmentfault.com/a/1190000022623676