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常用的JavaScript WEB操作方法分享_javascript技巧

程序员文章站 2022-04-13 13:58:31
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数组方法集
Angela.array = {  //# 数组方法
  // index, 返回位置! 不存在则返回 -1;
  index: function (t, arr) { //# 返回当前值所在数组的位置
    if (arr.indexOf) {
      return arr.indexOf(t);
    }
    for (var i = arr.length ; i--;) {
      if (arr[i] === t) {
        return i * 1;
      }
    };
    return -1;
  }
  //返回对象 的 键值! 返回值 类型为数组。
  , getKey: function (data) { //# 返回对象所有的键值
    var arr = []
      , k
    ;
    for (k in data) {
      arr.push(k);
    };
    return arr;
  }
  //从数组中 随机取出 一个值
  , random: function (arrays) { //# 从数组中 随机取出 一个值
    arrays = arrays || [];
    var len = arrays.length
      , index = Tydic.math.randInt(0, len - 1)
    ;
    return arrays[index] || '';
  }
  // 一维 数组去重
  , unique: function (array) { //#一维数组去重
    array = array || [];
    for (var i = 0, len = array.length; i 

cookie方法集

Angela.cookie = { //# Cookie
  // 浏览器是够支持 cookie
  enable: !!navigator.cookieEnabled
  //读取COOKIE
  , get: function (name) { //#读取 cookie
    var reg = new RegExp("(^| )" + name + "(?:=([^;]*))?(;|$)")
      , val = document.cookie.match(reg)
    ;
    return val ? (val[2] ? unescape(val[2]) : "") : '';
  }
  //写入COOKIES
  , set: function (name, value, expires, path, domain, secure) { //# 写入 cookie
    var exp = new Date()
      , expires = arguments[2] || null
      , path = arguments[3] || "/"
      , domain = arguments[4] || null
      , secure = arguments[5] || false
    ;
    expires ? exp.setMinutes(exp.getMinutes() + parseInt(expires)) : "";
    document.cookie = name + '=' + escape(value) + (expires ? ';expires=' + exp.toGMTString() : '') + (path ? ';path=' + path : '') + (domain ? ';domain=' + domain : '') + (secure ? ';secure' : '');
  }
  //删除cookie
  , del: function (name, path, domain, secure) { //#删除 cookie
    var value = $getCookie(name);
    if (value != null) {
      var exp = new Date();
      exp.setMinutes(exp.getMinutes() - 1000);
      path = path || "/";
      document.cookie = name + '=;expires=' + exp.toGMTString() + (path ? ';path=' + path : '') + (domain ? ';domain=' + domain : '') + (secure ? ';secure' : '');
    }
  }
};

url方法集

Angela.url = { //#URL
  //参数:变量名,url为空则表从当前页面的url中取
  getQuery: function (name, url) {
    var u = arguments[1] || window.location.search
      , reg = new RegExp("(^|&)" + name + "=([^&]*)(&|$)")
      , r = u.substr(u.indexOf("?") + 1).match(reg)
    ;
    return r != null ? r[2] : "";
  }
  , getHash: function (name, url) { //# 获取 hash值
    var u = arguments[1] || location.hash;
    var reg = new RegExp("(^|&)" + name + "=([^&]*)(&|$)");
    var r = u.substr(u.indexOf("#") + 1).match(reg);
    if (r != null) {
      return r[2];
    }
    return "";
  }
  , parse: function (url) { //# 解析URL
    var a = document.createElement('a');
    url = url || document.location.href;
    a.href = url;
    return {
      source: url
      , protocol: a.protocol.replace(':', '')
      , host: a.hostname
      , port: a.port
      , query: a.search
      , file: (a.pathname.match(/([^\/?#]+)$/i) || [, ''])[1]
      , hash: a.hash.replace('#', '')
      , path: a.pathname.replace(/^([^\/])/, '/$1')
      , relative: (a.href.match(/tps?:\/\/[^\/]+(.+)/) || [, ''])[1]
      , segments: a.pathname.replace(/^\//, '').split('/')
    };
  }
};

正则表达式方法集

Angela.regExp = { //# 字符串匹配
  //是否为 数字!整数,浮点数
  isNum: function (num) { //# 是否为数组
    return !isNaN(num);
  }
  , isEmail: function (mail) {//# 是否为 邮箱
    return /^([a-z0-9]+[_\-\.]?)*[a-z0-9]+@([a-z0-9]+[_\-\.]?)*[a-z0-9]+\.[a-z]{2,5}$/i.test(mail);
  }
  , isIdCard: function (card) { //# 是否为 身份证
    return /^(\d{14}|\d{17})(\d|[xX])$/.test(card);
  }
  , isMobile: function (mobile) { //# 是否为 手机
    return /^0*1\d{10}$/.test(mobile);
  }
  , isQQ: function (qq) { //# 是否为 QQ
    return /^[1-9]\d{4,10}$/.test(qq);
  }
  , isTel: function (tel) { //# 是否为 电话
    return /^\d{3,4}-\d{7,8}(-\d{1,6})?$/.text(tel);
  }
  , isUrl: function (url) { //# 是否为 URL
    return /https?:\/\/[a-z0-9\.\-]{1,255}\.[0-9a-z\-]{1,255}/i.test(url);
  }
  , isColor: function (color) { //# 是否为 16进制颜色
    return /#([\da-f]{3}){1,2}$/i.test(color);
  }
  //@id : 身份证 ,
  // @now : 当前时间 如:new Date('2013/12/12') , '2013/12/12'
  // @age : 允许的年龄
  , isAdult: function (id, allowAge, now) { //# 是否年龄是否成年
    var age = 0 // 用户 年月日
      , nowDate = 0 //当前年月日
    ;
    allowAge = parseFloat(allowAge) || 18;
    now = typeof now == 'string' ? new Date(now) : (now || new Date());


    if (!this.isIdCard(id)) {
      return false;
    }
    //15位身份证
    if (15 == id.length) {
      age = '19' + id.slice(6, 6);
    } else {
      age = id.slice(6, 14);
    }
    // 类型转换 整型
    age = ~~age;
    nowDate = ~~(Tydic.date.format('YYYYMMDD', now));
    //比较年龄
    if (nowDate - age 

字符串方法集

Angela.string = { //# 字符串
  codeHtml: function (content) { //# 转义 HTML 字符
    return this.replace(content, {
      '&': "&"
      , '"': """
      , "'": '''
      , '': ">"
      , ' ': " "
      , '\t': "	"
      , '(': "("
      , ')': ")"
      , '*': "*"
      , '+': "+"
      , ',': ","
      , '-': "-"
      , '.': "."
      , '/': "/"
      , '?': "?"
      , '\\': "\"
      , '\n': "
" }); } //重复字符串 , repeat: function (word, length, end) { //# 重复字符串 end = end || ''; //加在末位 length = ~~length; return new Array(length * 1 + 1).join(word) + '' + end; } //增加前缀 , addPre: function (pre, word, size) { //# 补齐。如给数字前 加 0 pre = pre || '0'; size = parseInt(size) || 0; word = String(word || ''); var length = Math.max(0, size - word.length); return this.repeat(pre, length, word); } //去除两边空格 , trim: function (text) { //# 去除两边空格 return (text || '').replace(/^\s+|\s$/, ''); } //字符串替换 , replace: function (str, re) { //# 字符串替换 str = str || ''; for (var key in re) { replace(key, re[key]); }; function replace(a, b) { var arr = str.split(a); str = arr.join(b); }; return str; } , xss: function (str, type) { //# XSS 转义 //空过滤 if (!str) { return str === 0 ? "0" : ""; } switch (type) { case "html": //过滤html字符串中的XSS return str.replace(/[&'"\/\\\-\x00-\x09\x0b-\x0c\x1f\x80-\xff]/g, function (r) { return "" + r.charCodeAt(0) + ";" }).replace(/ /g, " ").replace(/\r\n/g, "
").replace(/\n/g, "
").replace(/\r/g, "
"); break; case "htmlEp": //过滤DOM节点属性中的XSS return str.replace(/[&'"\/\\\-\x00-\x1f\x80-\xff]/g, function (r) { return "" + r.charCodeAt(0) + ";" }); break; case "url": //过滤url return escape(str).replace(/\+/g, "%2B"); break; case "miniUrl": return str.replace(/%/g, "%25"); break; case "script": return str.replace(/[\\"']/g, function (r) { return "\\" + r; }).replace(/%/g, "\\x25").replace(/\n/g, "\\n").replace(/\r/g, "\\r").replace(/\x01/g, "\\x01"); break; case "reg": return str.replace(/[\\\^\$\*\+\?\{\}\.\(\)\[\]]/g, function (a) { return "\\" + a; }); break; default: return escape(str).replace(/[&'"\/\\\-\x00-\x09\x0b-\x0c\x1f\x80-\xff]/g, function (r) { return "" + r.charCodeAt(0) + ";" }).replace(/ /g, " ").replace(/\r\n/g, "
").replace(/\n/g, "
").replace(/\r/g, "
"); break; } } // badword , 过滤敏感词 //@text : 要过滤的文本 , 类型 :字符串 //@words : 敏感词 ,类型,数组, 如 : ['你妹', '我丢' ,'我靠'] // 如果 用 正则匹配, text 长度 100万,words 100万,需要 4秒! , badWord: function (text, words) { //# 敏感词过滤 text = String(text || ''); words = words || []; var reg = new RegExp(words.join('|'), 'g') , _self = this; return text.replace(reg, function ($0) { var length = String($0 || '').length; return _self.repeat('*', length); }); } };

加密方法集

Angela.encrypt = { //# 加密
  md5: function (words) { //# md5 哈希算法
    /*
     * Crypto-JS 3.1.2
     * http://code.google.com/p/crypto-js
     */
    var CryptoJS = function (s, p) {
      var m = {}, l = m.lib = {}, n = function () { }, r = l.Base = { extend: function (b) { n.prototype = this; var h = new n; b && h.mixIn(b); h.hasOwnProperty("init") || (h.init = function () { h.$super.init.apply(this, arguments) }); h.init.prototype = h; h.$super = this; return h }, create: function () { var b = this.extend(); b.init.apply(b, arguments); return b }, init: function () { }, mixIn: function (b) { for (var h in b) b.hasOwnProperty(h) && (this[h] = b[h]); b.hasOwnProperty("toString") && (this.toString = b.toString) }, clone: function () { return this.init.prototype.extend(this) } }, q = l.WordArray = r.extend({ init: function (b, h) { b = this.words = b || []; this.sigBytes = h != p ? h : 4 * b.length }, toString: function (b) { return (b || t).stringify(this) }, concat: function (b) { var h = this.words, a = b.words, j = this.sigBytes; b = b.sigBytes; this.clamp(); if (j % 4) for (var g = 0; g >> 2] |= (a[g >>> 2] >>> 24 - 8 * (g % 4) & 255) >> 2] = a[g >>> 2]; else h.push.apply(h, a); this.sigBytes += b; return this }, clamp: function () { var b = this.words, h = this.sigBytes; b[h >>> 2] &= 4294967295 >> 2] >>> 24 - 8 * (j % 4) & 255; g.push((k >>> 4).toString(16)); g.push((k & 15).toString(16)) } return g.join("") }, parse: function (b) { for (var a = b.length, g = [], j = 0; j >> 3] |= parseInt(b.substr(j, 2), 16) >> 2] >>> 24 - 8 * (j % 4) & 255)); return g.join("") }, parse: function (b) { for (var a = b.length, g = [], j = 0; j >> 2] |= (b.charCodeAt(j) & 255) >> 32 - j) + k } function m(a, k, b, h, l, j, m) { a = a + (k & h | b & ~h) + l + m; return (a >> 32 - j) + k } function l(a, k, b, h, l, j, m) { a = a + (k ^ b ^ h) + l + m; return (a >> 32 - j) + k } function n(a, k, b, h, l, j, m) { a = a + (b ^ (k | ~h)) + l + m; return (a >> 32 - j) + k } for (var r = CryptoJS, q = r.lib, v = q.WordArray, t = q.Hasher, q = r.algo, a = [], u = 0; 64 > u; u++) a[u] = 4294967296 * s.abs(s.sin(u + 1)) | 0; q = q.MD5 = t.extend({
        _doReset: function () { this._hash = new v.init([1732584193, 4023233417, 2562383102, 271733878]) }, _doProcessBlock: function (g, k) {
          for (var b = 0; 16 > b; b++) { var h = k + b, w = g[h]; g[h] = (w >> 24) & 16711935 | (w >> 8) & 4278255360 } var b = this._hash.words, h = g[k + 0], w = g[k + 1], j = g[k + 2], q = g[k + 3], r = g[k + 4], s = g[k + 5], t = g[k + 6], u = g[k + 7], v = g[k + 8], x = g[k + 9], y = g[k + 10], z = g[k + 11], A = g[k + 12], B = g[k + 13], C = g[k + 14], D = g[k + 15], c = b[0], d = b[1], e = b[2], f = b[3], c = p(c, d, e, f, h, 7, a[0]), f = p(f, c, d, e, w, 12, a[1]), e = p(e, f, c, d, j, 17, a[2]), d = p(d, e, f, c, q, 22, a[3]), c = p(c, d, e, f, r, 7, a[4]), f = p(f, c, d, e, s, 12, a[5]), e = p(e, f, c, d, t, 17, a[6]), d = p(d, e, f, c, u, 22, a[7]), c = p(c, d, e, f, v, 7, a[8]), f = p(f, c, d, e, x, 12, a[9]), e = p(e, f, c, d, y, 17, a[10]), d = p(d, e, f, c, z, 22, a[11]), c = p(c, d, e, f, A, 7, a[12]), f = p(f, c, d, e, B, 12, a[13]), e = p(e, f, c, d, C, 17, a[14]), d = p(d, e, f, c, D, 22, a[15]), c = m(c, d, e, f, w, 5, a[16]), f = m(f, c, d, e, t, 9, a[17]), e = m(e, f, c, d, z, 14, a[18]), d = m(d, e, f, c, h, 20, a[19]), c = m(c, d, e, f, s, 5, a[20]), f = m(f, c, d, e, y, 9, a[21]), e = m(e, f, c, d, D, 14, a[22]), d = m(d, e, f, c, r, 20, a[23]), c = m(c, d, e, f, x, 5, a[24]), f = m(f, c, d, e, C, 9, a[25]), e = m(e, f, c, d, q, 14, a[26]), d = m(d, e, f, c, v, 20, a[27]), c = m(c, d, e, f, B, 5, a[28]), f = m(f, c, d, e, j, 9, a[29]), e = m(e, f, c, d, u, 14, a[30]), d = m(d, e, f, c, A, 20, a[31]), c = l(c, d, e, f, s, 4, a[32]), f = l(f, c, d, e, v, 11, a[33]), e = l(e, f, c, d, z, 16, a[34]), d = l(d, e, f, c, C, 23, a[35]), c = l(c, d, e, f, w, 4, a[36]), f = l(f, c, d, e, r, 11, a[37]), e = l(e, f, c, d, u, 16, a[38]), d = l(d, e, f, c, y, 23, a[39]), c = l(c, d, e, f, B, 4, a[40]), f = l(f, c, d, e, h, 11, a[41]), e = l(e, f, c, d, q, 16, a[42]), d = l(d, e, f, c, t, 23, a[43]), c = l(c, d, e, f, x, 4, a[44]), f = l(f, c, d, e, A, 11, a[45]), e = l(e, f, c, d, D, 16, a[46]), d = l(d, e, f, c, j, 23, a[47]), c = n(c, d, e, f, h, 6, a[48]), f = n(f, c, d, e, u, 10, a[49]), e = n(e, f, c, d,
                C, 15, a[50]), d = n(d, e, f, c, s, 21, a[51]), c = n(c, d, e, f, A, 6, a[52]), f = n(f, c, d, e, q, 10, a[53]), e = n(e, f, c, d, y, 15, a[54]), d = n(d, e, f, c, w, 21, a[55]), c = n(c, d, e, f, v, 6, a[56]), f = n(f, c, d, e, D, 10, a[57]), e = n(e, f, c, d, t, 15, a[58]), d = n(d, e, f, c, B, 21, a[59]), c = n(c, d, e, f, r, 6, a[60]), f = n(f, c, d, e, z, 10, a[61]), e = n(e, f, c, d, j, 15, a[62]), d = n(d, e, f, c, x, 21, a[63]); b[0] = b[0] + c | 0; b[1] = b[1] + d | 0; b[2] = b[2] + e | 0; b[3] = b[3] + f | 0
        }, _doFinalize: function () { var a = this._data, k = a.words, b = 8 * this._nDataBytes, h = 8 * a.sigBytes; k[h >>> 5] |= 128 >> 9 >> 24) & 16711935 | (l >> 8) & 4278255360; k[(h + 64 >>> 9 >> 24) & 16711935 | (b >> 8) & 4278255360; a.sigBytes = 4 * (k.length + 1); this._process(); a = this._hash; k = a.words; for (b = 0; 4 > b; b++) h = k[b], k[b] = (h >> 24) & 16711935 | (h >> 8) & 4278255360; return a }, clone: function () { var a = t.clone.call(this); a._hash = this._hash.clone(); return a }
      }); r.MD5 = t._createHelper(q); r.HmacMD5 = t._createHmacHelper(q)
    })(Math);
    return CryptoJS.MD5(words).toString();
  }
  // sha1
  , sha1: function (words) { //# sha1 哈希算法
    var CryptoJS = function (e, m) { var p = {}, j = p.lib = {}, l = function () { }, f = j.Base = { extend: function (a) { l.prototype = this; var c = new l; a && c.mixIn(a); c.hasOwnProperty("init") || (c.init = function () { c.$super.init.apply(this, arguments) }); c.init.prototype = c; c.$super = this; return c }, create: function () { var a = this.extend(); a.init.apply(a, arguments); return a }, init: function () { }, mixIn: function (a) { for (var c in a) a.hasOwnProperty(c) && (this[c] = a[c]); a.hasOwnProperty("toString") && (this.toString = a.toString) }, clone: function () { return this.init.prototype.extend(this) } }, n = j.WordArray = f.extend({ init: function (a, c) { a = this.words = a || []; this.sigBytes = c != m ? c : 4 * a.length }, toString: function (a) { return (a || h).stringify(this) }, concat: function (a) { var c = this.words, q = a.words, d = this.sigBytes; a = a.sigBytes; this.clamp(); if (d % 4) for (var b = 0; b >> 2] |= (q[b >>> 2] >>> 24 - 8 * (b % 4) & 255) >> 2] = q[b >>> 2]; else c.push.apply(c, q); this.sigBytes += a; return this }, clamp: function () { var a = this.words, c = this.sigBytes; a[c >>> 2] &= 4294967295 >> 2] >>> 24 - 8 * (d % 4) & 255; b.push((f >>> 4).toString(16)); b.push((f & 15).toString(16)) } return b.join("") }, parse: function (a) { for (var c = a.length, b = [], d = 0; d >> 3] |= parseInt(a.substr(d, 2), 16) >> 2] >>> 24 - 8 * (d % 4) & 255)); return b.join("") }, parse: function (a) { for (var c = a.length, b = [], d = 0; d >> 2] |= (a.charCodeAt(d) & 255)  a; a++) { if (16 > a) l[a] = f[n + a] | 0; else { var c = l[a - 3] ^ l[a - 8] ^ l[a - 14] ^ l[a - 16]; l[a] = c >> 31 } c = (h >> 27) + j + l[a]; c = 20 > a ? c + ((g & e | ~g & k) + 1518500249) : 40 > a ? c + ((g ^ e ^ k) + 1859775393) : 60 > a ? c + ((g & e | g & k | e & k) - 1894007588) : c + ((g ^ e ^ k) - 899497514); j = k; k = e; e = g >> 2; g = h; h = c } b[0] = b[0] + h | 0; b[1] = b[1] + g | 0; b[2] = b[2] + e | 0; b[3] = b[3] + k | 0; b[4] = b[4] + j | 0 }, _doFinalize: function () { var f = this._data, e = f.words, b = 8 * this._nDataBytes, h = 8 * f.sigBytes; e[h >>> 5] |= 128 >> 9 >> 9 

日期方法集

Angela.date = { //# 日期时间
  //@s : 开始时间
  //@e : 结束时间
  //@n : 当前时间 , n 的格式为 毫秒数
  isInArea: function (s, e, n) { //# 判断时间区域
    var start = this.parse(s),
      end = this.parse(e),
      now = parseFloat(n) || new Date()
    ;
    start = Math.min(start, end);
    end = Math.max(start, end);
    return now >= start && now 

浏览器检测方法集

Angela.browser = { //#浏览器
  browsers: { //# 浏览器内核类别
    weixin: /micromessenger(\/[\d\.]+)*/  //微信内置浏览器
    , mqq: /mqqbrowser(\/[\d\.]+)*/    //手机QQ浏览器
    , uc: /ucbrowser(\/[\d\.]+)*/      //UC浏览器
    , chrome: /(?:chrome|crios)(\/[\d\.]+)*/ //chrome浏览器
    , firefox: /firefox(\/[\d\.]+)*/     //火狐浏览器
    , opera: /opera(\/|\s)([\d\.]+)*/   //欧朋浏览器
    , sougou: /sogoumobilebrowser(\/[\d\.]+)*/  //搜狗手机浏览器
    , baidu: /baidubrowser(\/[\d\.]+)*/     //百度手机浏览器
    , 360: /360browser([\d\.]*)/             //360浏览器
    , safari: /safari(\/[\d\.]+)*/    //苹果浏览器
    , ie: /msie\s([\d\.]+)*/  // ie 浏览器
  }
  //@errCall : 错误回调
  , addFav: function (url, title, errCall) { //#加入收藏夹
    try {
      window.external.addFavorite(url, title);
    } catch (e) {
      try {
        window.sidebar.addPanel(title, url, '');
      } catch (e) {
        errCall();
      }
    }
  },
  //浏览器版本
  coreInit: function () { //#noadd
    var i = null
      , browsers = this.browsers
      , ua = window.navigator.userAgent.toLowerCase()
      , brower = ''
      , pos = 1
    ;
    for (i in browsers) {
      if (brower = ua.match(browsers[i])) {
        if (i == 'opera') {
          pos = 2;
        } else {
          pos = 1;
        }
        this.version = (brower[pos] || '').replace(/[\/\s]+/, '');
        this.core = i;
        return i;
      }
    }
  }
  // 检测IE版本 !仅支持IE: 5,6,7,8,9 版本
  , ie: (function () { //# 检测IE版本 !仅支: ie5,6,7,8,9
    var v = 3, div = document.createElement('div'), all = div.getElementsByTagName('i');
    while (
      div.innerHTML = '',
        all[0]
      );
    return v > 4 ? v : false;
  })()
  , isWebkit: /webkit/i.test(navigator.userAgent)
  

};

json方法

Angela.json = { //# json 对象
  // 字符串 变为 json 对象
  parse: function (data) { //# 格式化字符串,变为 json 对象
    var // JSON RegExp
      rvalidchars = /^[\],:{}\s]*$/
      , rvalidbraces = /(?:^|:|,)(?:\s*\[)+/g
      , rvalidescape = /\\(?:["\\\/bfnrt]|u[\da-fA-F]{4})/g
      , rvalidtokens = /"[^"\\\r\n]*"|true|false|null|-?(?:\d+\.|)\d+(?:[eE][+-]?\d+|)/g
    ;
    if (window.JSON && window.JSON.parse) {
      return window.JSON.parse(data);
    }

    if (data === null) {
      return data;
    }
    if (typeof data === "string") {
      data = data.replace(/^\s+|\s+$/g, '');
      if (data && rvalidchars.test(data.replace(rvalidescape, "@")
        .replace(rvalidtokens, "]")
        .replace(rvalidbraces, ""))) {
        return (new Function("return " + data))();
      }
    }
    return '';
  }
};

extend方法

Angela.extend = function () { //# 对象扩展
  var target = arguments[0] || {}
    , i = 1
    , length = arguments.length
    , options
  ;
  if (typeof target != "object" && typeof target != "function")
    target = {};
  for (; i 

类型判断的方法

/*
*判断变量val是不是整数类型
*/
function isNumber(val) {
  return typeof val === 'number' && isFinite(val);
}

/*
*判断变量val是不是布尔类型
*/
function isBoolean(val) {
  return typeof val === 'boolean';
}

/*
*判断变量val是不是字符串类型
*/
function isString (val) {
  return typeof val === 'string';
}

/*
*判断变量val是不是undefined
*/
function isUndefined(val) {
  return typeof val === 'undefined';
}

/*
*判断变量val是不是对象
*/
function isObj(str) {
  if (str===null||typeof str==='undefined') {
    return false;
  }
  return typeof str === 'object';
}

/*
*判断变量val是不是null
*/
function isNull(val) {
  return val === null;
}

/*
*判断变量arr是不是数组
*方法一
*/
function isArray1(arr) {
  return Object.prototype.toString.apply(arr) === '[object Array]';
}

/*
*判断变量arr是不是数组
*方法二
*/
function isArray2(arr) {
  if (arr === null || typeof arr === 'undefined') {
    return false;
  }
  return arr.constructor === Array;
}