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Summarize the JS functions commonly used in front-end development (2)
- 王林forward
- 2019-08-21 17:27:312570browse
本文接上一篇：总结前端开发中常用的JS功能函数（一）
25、unique： 数组去重，返回一个新数组
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
}26、Set简单实现
window.Set = window.Set || (function () {
function Set(arr) {
this.items = arr ? unique(arr) : [];
this.size = this.items.length; // Array的大小
}
Set.prototype = {
add: function (value) {
// 添加元素,若元素已存在,则跳过，返回 Set 结构本身。
if (!this.has(value)) {
this.items.push(value);
this.size++;
}
return this;
},
clear: function () {
//清除所有成员，没有返回值。
this.items = []
this.size = 0
},
delete: function (value) {
//删除某个值，返回一个布尔值，表示删除是否成功。
return this.items.some((v, i) => {
if(v === value){
this.items.splice(i,1)
return true
}
return false
})
},
has: function (value) {
//返回一个布尔值，表示该值是否为Set的成员。
return this.items.some(v => v === value)
},
values: function () {
return this.items
},
}
return Set;
}());27、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
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) ==> 12312312328、dateFormater：格式化时间
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) ==> 20190626183029、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
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') ==> 2019-06-2630、getPropByPath：根据字符串路径获取对象属性：‘obj[0].count’
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
};
};31、GetUrlParam：获取Url参数，返回一个对象
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"}32、downloadFile：base64数据导出文件，文件下载
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);
}
}33、toFullScreen：全屏
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");
}34、exitFullscreen：退出全屏
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");
}35、requestAnimationFrame：window动画
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);
}36、_isNaN：检查数据是否是非数字值
function _isNaN(v){
return !(typeof v === 'string' || typeof v === 'number') || isNaN(v)
}37、max：求取数组中非NaN数据中的最大值
function max(arr){
arr = arr.filter(item => !_isNaN(item))
return arr.length ? Math.max.apply(null, arr) : undefined
}
//max([1, 2, '11', null, 'fdf', []]) ==> 1138、min：求取数组中非NaN数据中的最小值
function min(arr){
arr = arr.filter(item => !_isNaN(item))
return arr.length ? Math.min.apply(null, arr) : undefined
}
//min([1, 2, '11', null, 'fdf', []]) ==> 139、random：返回一个lower-upper直接的随机数。（lower、upper无论正负与大小，但必须是非NaN的数据）
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) ==> -1.447432545236194540、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
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;
}41、Object.values:返回一个给定对象自身的所有可枚举属性值的数组
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;
}42、arr.fill:使用value值填充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
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]43、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，否则返回false，可指定开始查询的位置
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;
}44、返回数组中通过测试（函数fn内判断）的第一个元素的值
Array.prototype.find = Array.prototype.find || function find(fn, ctx) {
ctx = ctx || this;
let result;
ctx.some((value, index, arr), thisValue) => {
return fn(value, index, arr) ? (result = value, true) : false
})
return result
}45、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
Array.prototype.findIndex = Array.prototype.findIndex || function findIndex(fn, ctx){
ctx = ctx || this
let result;
ctx.some((value, index, arr), thisValue) => {
return fn(value, index, arr) ? (result = index, true) : false
})
return result
}46、performance.timing:利用performance.timing进行性能分析
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) + '%')
}
})
}47、禁止某些键盘事件
document.addEventListener('keydown', function(event) {
return !(
112 == event.keyCode || //禁止F1
123 == event.keyCode || //禁止F12
event.ctrlKey && 82 == event.keyCode || //禁止ctrl+R
event.ctrlKey && 18 == event.keyCode || //禁止ctrl+N
event.shiftKey && 121 == event.keyCode || //禁止shift+F10
event.altKey && 115 == event.keyCode || //禁止alt+F4
"A" == event.srcElement.tagName && event.shiftKey //禁止shift+点击a标签
) || （event.returnValue = false）
});48、禁止右键、选择、复制
['contextmenu', 'selectstart', 'copy'].forEach(function(ev) {
document.addEventListener(ev, function(event) {
return event.returnValue = false;
})
});以上两篇文章就是整理的48个前端开发常用函数，欢迎大家继续补充。谢谢！
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