JS开发常用工具函数

发布 : 2019-07-02 浏览 :

isStatic:检测数据是不是除了symbol外的原始数据

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function isStatic(value) {
return(
typeof value === 'string' ||
typeof value === 'number' ||
typeof value === 'boolean' ||
typeof value === 'undefined' ||
value === null
)
}

isPrimitive:检测数据是不是原始数据

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function isPrimitive(value) {
return isStatic(value) || typeof value === 'symbol'
}

isObject:判断数据是不是引用类型的数据 (例如: arrays, functions, objects, regexes, new Number(0),以及 new String(‘’))

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function isObject(value) {
let type = typeof value;
return value != null && (type == 'object' || type == 'function');
}

isObjectLike:检查 value 是否是 类对象。 如果一个值是类对象,那么它不应该是 null,而且 typeof 后的结果是 “object”

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function isObjectLike(value) {
return value != null && typeof value == 'object';
}

getRawType:获取数据类型,返回结果为 Number、String、Object、Array等

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function getRawType(value) {
return Object.prototype.toString.call(value).slice(8, -1)
}
//getoRawType([]) ==> Array

isPlainObject:判断数据是不是Object类型的数据

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function isPlainObject(obj) {
return Object.prototype.toString.call(obj) === '[object Object]'
}

isArray:判断数据是不是数组类型的数据

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function isArray(arr) {
return Object.prototype.toString.call(arr) === '[object Array]'
}
将isArray挂载到Array上
Array.isArray = Array.isArray || isArray;

isRegExp:判断数据是不是正则对象

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function isRegExp(value) {
return Object.prototype.toString.call(value) === '[object RegExp]'
}

isDate:判断数据是不是时间对象

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function isDate(value) {
return Object.prototype.toString.call(value) === '[object Date]'
}

isNative:判断 value 是不是浏览器内置函数

内置函数toString后的主体代码块为 [native code] ,而非内置函数则为相关代码,所以非内置函数可以进行拷贝(toString后掐头去尾再由Function转)

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function isNative(value) {
return typeof value === 'function' && /native code/.test(value.toString())
}

isFunction:检查 value 是不是函数

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function isFunction(value) {
return Object.prototype.toString.call(value) === '[object Function]'
}

isLength:检查 value 是否为有效的类数组长度

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function isLength(value) {
return typeof value == 'number' && value > -1 && value % 1 == 0 && value <= Number.MAX_SAFE_INTEGER;
}

isArrayLike:检查 value 是否是类数组

如果一个值被认为是类数组,那么它不是一个函数,并且value.length是个整数,大于等于 0,小于或等于 Number.MAX_SAFE_INTEGER。这里字符串也将被当作类数组

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function isArrayLike(value) {
return value != null && isLength(value.length) && !isFunction(value);
}

isEmpty:检查 value 是否为空

如果是null,直接返回true;如果是类数组,判断数据长度;如果是Object对象,判断是否具有属性;如果是其他数据,直接返回false(也可改为返回true)

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function isEmpty(value) {
if (value == null) {
return true;
}
if (isArrayLike(value)) {
return !value.length;
}else if(isPlainObject(value)){
for (let key in value) {
if (hasOwnProperty.call(value, key)) {
return false;
}
}
return true;
}
return false;
}

cached:记忆函数:缓存函数的运算结果

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function cached(fn) {
let cache = Object.create(null);
return function cachedFn(str) {
let hit = cache[str];
return hit || (cache[str] = fn(str))
}
}

camelize:横线转驼峰命名

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let camelizeRE = /-(\w)/g;
function camelize(str) {
return str.replace(camelizeRE, function(_, c) {
return c ? c.toUpperCase() : '';
})
}
//ab-cd-ef ==> abCdEf
//使用记忆函数
let _camelize = cached(camelize)

hyphenate:驼峰命名转横线命名:拆分字符串,使用 - 相连,并且转换为小写

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let hyphenateRE = /\B([A-Z])/g;
function hyphenate(str){
return str.replace(hyphenateRE, '-$1').toLowerCase()
}
//abCd ==> ab-cd
//使用记忆函数
let _hyphenate = cached(hyphenate);

capitalize:字符串首位大写

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function capitalize(str){
return str.charAt(0).toUpperCase() + str.slice(1)
}
// abc ==> Abc
//使用记忆函数
let _capitalize = cached(capitalize)

Object.assign:对象属性复制,浅拷贝

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Object.assign = Object.assign || function(){
if(arguments.length == 0) throw new TypeError('Cannot convert undefined or null to object');

let target = arguments[0],
args = Array.prototype.slice.call(arguments, 1),
key
args.forEach(function(item){
for(key in item){
item.hasOwnProperty(key) && ( target[key] = item[key] )
}
})
return target
}

使用Object.assign可以浅克隆一个对象:

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let clone = Object.assign({}, target)

简单的深克隆可以使用JSON.parse()和JSON.stringify(),这两个api是解析json数据的,所以只能解析除symbol外的原始类型及数组和对象

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let clone = JSON.parse( JSON.stringify(target) )

clone:克隆数据,可深度克隆

这里列出了原始类型,时间、正则、错误、数组、对象的克隆规则,其他的可自行补充

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function clone(value, deep){
if(isPrimitive(value)){
return value
}

if (isArrayLike(value)) { //是类数组
value = Array.prototype.slice.call(value)
return value.map(item => deep ? clone(item, deep) : item)
}else if(isPlainObject(value)){ //是对象
let target = {}, key;
for (key in value) {
value.hasOwnProperty(key) && ( target[key] = deep ? clone(value[key], deep) : value[key] )
}
}

let type = getRawType(value)

switch(type){
case 'Date':
case 'RegExp':
case 'Error': value = new window[type](value); break;
}
return value
}

识别各种浏览器及平台

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//运行环境是浏览器
let inBrowser = typeof window !== 'undefined';
//运行环境是微信
let inWeex = typeof WXEnvironment !== 'undefined' && !!WXEnvironment.platform;
let weexPlatform = inWeex && WXEnvironment.platform.toLowerCase();
//浏览器 UA 判断
let UA = inBrowser && window.navigator.userAgent.toLowerCase();
let isIE = UA && /msie|trident/.test(UA);
let isIE9 = UA && UA.indexOf('msie 9.0') > 0;
let isEdge = UA && UA.indexOf('edge/') > 0;
let isAndroid = (UA && UA.indexOf('android') > 0) || (weexPlatform === 'android');
let isIOS = (UA && /iphone|ipad|ipod|ios/.test(UA)) || (weexPlatform === 'ios');
let isChrome = UA && /chrome\/\d+/.test(UA) && !isEdge;

getExplorerInfo:获取浏览器信息

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function getExplorerInfo() {
let t = navigator.userAgent.toLowerCase();
return 0 <= t.indexOf("msie") ? { //ie < 11
type: "IE",
version: Number(t.match(/msie ([\d]+)/)[1])
} : !!t.match(/trident\/.+?rv:(([\d.]+))/) ? { // ie 11
type: "IE",
version: 11
} : 0 <= t.indexOf("edge") ? {
type: "Edge",
version: Number(t.match(/edge\/([\d]+)/)[1])
} : 0 <= t.indexOf("firefox") ? {
type: "Firefox",
version: Number(t.match(/firefox\/([\d]+)/)[1])
} : 0 <= t.indexOf("chrome") ? {
type: "Chrome",
version: Number(t.match(/chrome\/([\d]+)/)[1])
} : 0 <= t.indexOf("opera") ? {
type: "Opera",
version: Number(t.match(/opera.([\d]+)/)[1])
} : 0 <= t.indexOf("Safari") ? {
type: "Safari",
version: Number(t.match(/version\/([\d]+)/)[1])
} : {
type: t,
version: -1
}
}

isPCBroswer:检测是否为PC端浏览器模式

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function isPCBroswer() {
let e = navigator.userAgent.toLowerCase()
, t = "ipad" == e.match(/ipad/i)
, i = "iphone" == e.match(/iphone/i)
, r = "midp" == e.match(/midp/i)
, n = "rv:1.2.3.4" == e.match(/rv:1.2.3.4/i)
, a = "ucweb" == e.match(/ucweb/i)
, o = "android" == e.match(/android/i)
, s = "windows ce" == e.match(/windows ce/i)
, l = "windows mobile" == e.match(/windows mobile/i);
return !(t || i || r || n || a || o || s || l)
}

unique:数组去重,返回一个新数组

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function unique(arr){
if(!isArrayLink(arr)){ //不是类数组对象
return arr
}
let result = []
let objarr = []
let obj = Object.create(null)

arr.forEach(item => {
if(isStatic(item)){//是除了symbol外的原始数据
let key = item + '_' + getRawType(item);
if(!obj[key]){
obj[key] = true
result.push(item)
}
}else{//引用类型及symbol
if(!objarr.includes(item)){
objarr.push(item)
result.push(item)
}
}
})

return resulte
}

Set简单实现

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function unique(arr){
if(!isArrayLink(arr)){ //不是类数组对象
return arr
}
let result = []
let objarr = []
let obj = Object.create(null)

arr.forEach(item => {
if(isStatic(item)){//是除了symbol外的原始数据
let key = item + '_' + getRawType(item);
if(!obj[key]){
obj[key] = true
result.push(item)
}
}else{//引用类型及symbol
if(!objarr.includes(item)){
objarr.push(item)
result.push(item)
}
}
})

return resulte
}

repeat:生成一个重复的字符串,有n个str组成,可修改为填充为数组等

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function repeat(str, n) {
let res = '';
while(n) {
if(n % 2 === 1) {
res += str;
}
if(n > 1) {
str += str;
}
n >>= 1;
}
return res
};
//repeat('123',3) ==> 123123123

dateFormater:格式化时间

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function dateFormater(formater, t){
let date = t ? new Date(t) : new Date(),
Y = date.getFullYear() + '',
M = date.getMonth() + 1,
D = date.getDate(),
H = date.getHours(),
m = date.getMinutes(),
s = date.getSeconds();
return formater.replace(/YYYY|yyyy/g,Y)
.replace(/YY|yy/g,Y.substr(2,2))
.replace(/MM/g,(M<10?'0':'') + M)
.replace(/DD/g,(D<10?'0':'') + D)
.replace(/HH|hh/g,(H<10?'0':'') + H)
.replace(/mm/g,(m<10?'0':'') + m)
.replace(/ss/g,(s<10?'0':'') + s)
}
// dateFormater('YYYY-MM-DD HH:mm', t) ==> 2019-06-26 18:30
// dateFormater('YYYYMMDDHHmm', t) ==> 201906261830

dateStrForma:将指定字符串由一种时间格式转化为另一种

from的格式应对应str的位置

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function dateStrForma(str, from, to){
//'20190626' 'YYYYMMDD' 'YYYY年MM月DD日'
str += ''
let Y = ''
if(~(Y = from.indexOf('YYYY'))){
Y = str.substr(Y, 4)
to = to.replace(/YYYY|yyyy/g,Y)
}else if(~(Y = from.indexOf('YY'))){
Y = str.substr(Y, 2)
to = to.replace(/YY|yy/g,Y)
}

let k,i
['M','D','H','h','m','s'].forEach(s =>{
i = from.indexOf(s+s)
k = ~i ? str.substr(i, 2) : ''
to = to.replace(s+s, k)
})
return to
}
// dateStrForma('20190626', 'YYYYMMDD', 'YYYY年MM月DD日') ==> 2019年06月26日
// dateStrForma('121220190626', '----YYYYMMDD', 'YYYY年MM月DD日') ==> 2019年06月26日
// dateStrForma('2019年06月26日', 'YYYY年MM月DD日', 'YYYYMMDD') ==> 20190626

// 一般的也可以使用正则来实现
//'2019年06月26日'.replace(/(\d{4})年(\d{2})月(\d{2})日/, '$1-$2-$3') ==> 2019-06-26

getPropByPath:根据字符串路径获取对象属性 : ‘obj[0].count’

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function getPropByPath(obj, path, strict) {
let tempObj = obj;
path = path.replace(/\[(\w+)\]/g, '.$1'); //将[0]转化为.0
path = path.replace(/^\./, ''); //去除开头的.

let keyArr = path.split('.'); //根据.切割
let i = 0;
for (let len = keyArr.length; i < len - 1; ++i) {
if (!tempObj && !strict) break;
let key = keyArr[i];
if (key in tempObj) {
tempObj = tempObj[key];
} else {
if (strict) {//开启严格模式,没找到对应key值,抛出错误
throw new Error('please transfer a valid prop path to form item!');
}
break;
}
}
return {
o: tempObj, //原始数据
k: keyArr[i], //key值
v: tempObj ? tempObj[keyArr[i]] : null // key值对应的值
};
};

GetUrlParam:获取Url参数,返回一个对象

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function GetUrlParam(){
let url = document.location.toString();
let arrObj = url.split("?");
let params = Object.create(null)
if (arrObj.length > 1){
arrObj = arrObj[1].split("&");
arrObj.forEach(item=>{
item = item.split("=");
params[item[0]] = item[1]
})
}
return params;
}
// ?a=1&b=2&c=3 ==> {a: "1", b: "2", c: "3"}

downloadFile:base64数据导出文件,文件下载

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function downloadFile(filename, data){
let DownloadLink = document.createElement('a');

if ( DownloadLink ){
document.body.appendChild(DownloadLink);
DownloadLink.style = 'display: none';
DownloadLink.download = filename;
DownloadLink.href = data;

if ( document.createEvent ){
let DownloadEvt = document.createEvent('MouseEvents');

DownloadEvt.initEvent('click', true, false);
DownloadLink.dispatchEvent(DownloadEvt);
}
else if ( document.createEventObject )
DownloadLink.fireEvent('onclick');
else if (typeof DownloadLink.onclick == 'function' )
DownloadLink.onclick();

document.body.removeChild(DownloadLink);
}
}

toFullScreen:全屏

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function toFullScreen(){
let elem = document.body;
elem.webkitRequestFullScreen
? elem.webkitRequestFullScreen()
: elem.mozRequestFullScreen
? elem.mozRequestFullScreen()
: elem.msRequestFullscreen
? elem.msRequestFullscreen()
: elem.requestFullScreen
? elem.requestFullScreen()
: alert("浏览器不支持全屏");
}

exitFullscreen:退出全屏

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function exitFullscreen(){
let elem = parent.document;
elem.webkitCancelFullScreen
? elem.webkitCancelFullScreen()
: elem.mozCancelFullScreen
? elem.mozCancelFullScreen()
: elem.cancelFullScreen
? elem.cancelFullScreen()
: elem.msExitFullscreen
? elem.msExitFullscreen()
: elem.exitFullscreen
? elem.exitFullscreen()
: alert("切换失败,可尝试Esc退出");
}

requestAnimationFrame:window动画

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window.requestAnimationFrame = window.requestAnimationFrame ||
window.webkitRequestAnimationFrame ||
window.mozRequestAnimationFrame ||
window.msRequestAnimationFrame ||
window.oRequestAnimationFrame ||
function (callback) {
//为了使setTimteout的尽可能的接近每秒60帧的效果
window.setTimeout(callback, 1000 / 60);
};

window.cancelAnimationFrame = window.cancelAnimationFrame ||
Window.webkitCancelAnimationFrame ||
window.mozCancelAnimationFrame ||
window.msCancelAnimationFrame ||
window.oCancelAnimationFrame ||
function (id) {
//为了使setTimteout的尽可能的接近每秒60帧的效果
window.clearTimeout(id);
}

_isNaN:检查数据是否是非数字值

原生的isNaN会把参数转换成数字(valueof),而null、true、false以及长度小于等于1的数组(元素为非NaN数据)会被转换成数字,这不是我想要的。Symbol类型的数据不具有valueof接口,所以isNaN会抛出错误,这里放在后面,可避免错误

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function _isNaN(v){
return !(typeof v === 'string' || typeof v === 'number') || isNaN(v)
}

max:求取数组中非NaN数据中的最大值

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function max(arr){
arr = arr.filter(item => !_isNaN(item))
return arr.length ? Math.max.apply(null, arr) : undefined
}
//max([1, 2, '11', null, 'fdf', []]) ==> 11

min:求取数组中非NaN数据中的最小值

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function min(arr){
arr = arr.filter(item => !_isNaN(item))
return arr.length ? Math.min.apply(null, arr) : undefined
}
//min([1, 2, '11', null, 'fdf', []]) ==> 1

random:返回一个lower - upper之间的随机数

lower、upper无论正负与大小,但必须是非NaN的数据

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function random(lower, upper){
lower = +lower || 0
upper = +upper || 0
return Math.random() * (upper - lower) + lower;
}
//random(0, 0.5) ==> 0.3567039135734613
//random(2, 1) ===> 1.6718418553475423
//random(-2, -1) ==> -1.4474325452361945

Object.keys:返回一个由一个给定对象的自身可枚举属性组成的数组

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Object.keys = Object.keys || function keys(object) {
if(object === null || object === undefined){
throw new TypeError('Cannot convert undefined or null to object');
}
let result = []
if(isArrayLike(object) || isPlainObject(object)){
for (let key in object) {
object.hasOwnProperty(key) && ( result.push(key) )
}
}
return result
}

Object.keys:返回一个由一个给定对象的自身可枚举属性组成的数组

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Object.keys = Object.keys || function keys(object) {
if(object === null || object === undefined){
throw new TypeError('Cannot convert undefined or null to object');
}
let result = []
if(isArrayLike(object) || isPlainObject(object)){
for (let key in object) {
object.hasOwnProperty(key) && ( result.push(key) )
}
}
return result
}

Object.values:返回一个给定对象自身的所有可枚举属性值的数组

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Object.values = Object.values || function values(object) {
if(object === null || object === undefined){
throw new TypeError('Cannot convert undefined or null to object');
}
let result = []
if(isArrayLike(object) || isPlainObject(object)){
for (let key in object) {
object.hasOwnProperty(key) && ( result.push(object[key]) )
}
}
return result
}

arr.fill:使用 value 值来填充 array,从start位置开始, 到end位置结束(但不包含end位置),返回原数组

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Array.prototype.fill = Array.prototype.fill || function fill(value, start, end) {
let ctx = this
let length = ctx.length;

start = parseInt(start)
if(isNaN(start)){
start = 0
}else if (start < 0) {
start = -start > length ? 0 : (length + start);
}

end = parseInt(end)
if(isNaN(end) || end > length){
end = length
}else if (end < 0) {
end += length;
}

while (start < end) {
ctx[start++] = value;
}
return ctx;
}
//Array(3).fill(2) ===> [2, 2, 2]

arr.includes:用来判断一个数组是否包含一个指定的值,如果是返回 true,否则false,可指定开始查询的位置

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Array.prototype.includes = Array.prototype.includes || function includes(value, start){
let ctx = this
let length = ctx.length;

start = parseInt(start)
if(isNaN(start)){
start = 0
}else if (start < 0) {
start = -start > length ? 0 : (length + start);
}

let index = ctx.indexOf(value)

return index >= start;
}

arr.find:返回数组中通过测试(函数fn内判断)的第一个元素的值

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Array.prototype.find = Array.prototype.find || function find(fn, ctx){
fn = fn.bind(ctx)

let result;
this.some((value, index, arr), thisValue) => {
return fn(value, index, arr) ? (result = value, true) : false
})

return result
}

arr.findIndex :返回数组中通过测试(函数fn内判断)的第一个元素的下标

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Array.prototype.findIndex = Array.prototype.findIndex || function findIndex(fn, ctx){
fn = fn.bind(ctx)

let result;
this.some((value, index, arr), thisValue) => {
return fn(value, index, arr) ? (result = index, true) : false
})

return result
}

performance.timing:利用performance.timing进行性能分析

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window.onload = function(){
setTimeout(function(){
let t = performance.timing
console.log('DNS查询耗时 :' + (t.domainLookupEnd - t.domainLookupStart).toFixed(0))
console.log('TCP链接耗时 :' + (t.connectEnd - t.connectStart).toFixed(0))
console.log('request请求耗时 :' + (t.responseEnd - t.responseStart).toFixed(0))
console.log('解析dom树耗时 :' + (t.domComplete - t.domInteractive).toFixed(0))
console.log('白屏时间 :' + (t.responseStart - t.navigationStart).toFixed(0))
console.log('domready时间 :' + (t.domContentLoadedEventEnd - t.navigationStart).toFixed(0))
console.log('onload时间 :' + (t.loadEventEnd - t.navigationStart).toFixed(0))

if(t = performance.memory){
console.log('js内存使用占比 :' + (t.usedJSHeapSize / t.totalJSHeapSize * 100).toFixed(2) + '%')
}
})
}

禁止某些键盘事件

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document.addEventListener('keydown', function(event){
return !(
112 == event.keyCode || //F1
123 == event.keyCode || //F12
event.ctrlKey && 82 == event.keyCode || //ctrl + R
event.ctrlKey && 78 == event.keyCode || //ctrl + N
event.shiftKey && 121 == event.keyCode || //shift + F10
event.altKey && 115 == event.keyCode || //alt + F4
"A" == event.srcElement.tagName && event.shiftKey //shift + 点击a标签
) || (event.returnValue = false)
});

禁止右键、选择、复制

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['contextmenu', 'selectstart', 'copy'].forEach(function(ev){
document.addEventListener(ev, function(event){
return event.returnValue = false
})
});
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