javascript实用代码片段
持续积累中~
拓展原型
Function.prototype.method = function (name, extend) {
if (!this.prototype[name]) {
this.prototype[name] = extend;
}
return this;
};
实现继承·方法 1
Function.method("inherits", function (Parent) {
var _proptotype = Object.create(Parent.prototype);
_proptotype.constructor = this.prototype.constructor;
this.prototype = _proptotype;
return this;
});
实现继承·方法 2
function inherits(child, parent) {
var _proptotype = Object.create(parent.prototype);
_proptotype.constructor = child.prototype.constructor;
child.prototype = _proptotype;
return {
"child": child,
"parent": parent
};
}
实现继承·方法 3
//只创建临时构造函数一次
var inherit = (function () {
var F = function () {};
return function (C, P) {
F.prototype = P.prototype;
C.prototype = new F();
C.uber = P.prototype; // 存储超类
C.prototype.constructor = C; // 重置构造函数指针
}
})();
浅拷贝
function simpleCopy() {
var c = {};
for(var i in p) {
c[i] = p[i];
}
return c;
}
深拷贝
export function deepCopy(obj, parent = null) {
//parent用于递归循环引用爆栈处理
// 创建一个新对象
let result = new obj.constructor() //保持继承链
let keys = Object.keys(obj),
key = null,
temp = null,
_parent = parent
// 该字段若有父级则需要追溯该字段的父级
while (_parent) {
// 如果该字段引用了它的父级则为循环引用
if (_parent.originalParent === obj) {
return _parent.currentParent // 循环引用直接返回同级的新对象
}
_parent = _parent.parent
}
for (let i = 0; i < keys.length; i++) {
key = keys[i]
temp = obj[key]
if (temp && isType(temp) === 'date') {
result[key] = new Date(temp)
continue
}
if (temp && isType(temp) === 'regExp') {
result[key] = new RegExp(temp)
continue
}
// 若字段的值是一个对象/数组
if (temp && (isType(temp) === 'object' || isType(temp) === 'array')) {
// 递归执行深拷贝 将同级的待拷贝对象与新对象传递给 parent 方便追溯循环引用
result[key] = deepCopy(temp, {
originalParent: obj,
currentParent: result,
parent: parent
})
} else {
result[key] = temp
}
}
return result
}
带特性值的浅拷贝
function Composition(target, source){
var desc = Object.getOwnPropertyDescriptor;
var prop = Object.getOwnPropertyNames;
var def_prop=Object.defineProperty;
prop(source).forEach(function(key) {
def_prop(target, key, desc(source, key))
})
return target;
}
mixin 混合
function mix() {
var arg, prop, child = {};
for(arg = 0; arg < arguments.length; arg += 1) {
for(prop in arguments[arg]) {
if(arguments[arg].hasOwnProperty(prop)) {
child[prop] = arguments[arg][prop];
}
}
}
return child;
}
对象拓展
var MYAPP = MYAPP || {};
MYAPP.namespace = function(ns_string) {
var parts = ns_string.split('.'),
parent = MYAPP,
i;
//忽略第一个
if(parts[0] === "MYAPP") {
parts = parts.slice(1);
}
for(i = 0; i < parts.length; i += 1) {
//如果属性不存在,就创建
if(typeof parent[parts[i]] === "undefined") {
parent[parts[i]] = {};
}
parent = parent[parts[i]];
}
return parent;
};
MYAPP.namespace('once.upon.a.time.there.was.this.long.nested.property');
函数柯里化(Currying)
function curry(fn){
var args = Array.prototype.slice.call(arguments, 1);
return function(){
var innerArgs = Array.prototype.slice.call(arguments);
var finalArgs = args.concat(innerArgs);
return fn.apply(null, finalArgs);
};
}
function add(num1, num2){
return num1 + num2;
}
var curriedAdd = curry(add, 5);
alert(curriedAdd(3)); //8
函数节流
function throttle(fn, wait){
var timer;
return function(...args){
if(!timer){
timer = setTimeout(()=>timer=null, wait);
return fn.apply(this, args);
}
}
}
函数防抖
function debounce(fn, delay){
var timer = null;
return function(...args){
clearTimeout(timer);
timer = setTimeout(() => fn.apply(this, args), delay);
}
}
跨文件共享私有对象(模块互访)
var blogModule = (function(my) {
var _private = my._private = my._private || {},
_seal = my._seal = my._seal || function() {
delete my._private;
delete my._seal;
delete my._unseal;
},
_unseal = my._unseal = my._unseal || function() {
my._private = _private;
my._seal = _seal;
my._unseal = _unseal;
};
return my;
}(obj || {}));
类型判断
export function isType(obj, type) {
// tostring会返回对应不同的标签的构造函数
const toString = Object.prototype.toString
const map = {
'[object Boolean]': 'boolean',
'[object Number]': 'number',
'[object String]': 'string',
'[object Function]': 'function',
'[object Array]': 'array',
'[object Date]': 'date',
'[object RegExp]': 'regExp',
'[object Object]': 'object',
'[object Undefined]': 'undefined',
'[object Null]': 'null',
'[object Error]': 'error',
}
if (obj instanceof HTMLElement) {
return type ? type === 'element' : 'element'
}
return type ? type === map[toString.call(obj)] : map[toString.call(obj)]
}
软绑定[默认绑定可设置]
Function.prototype.softBind = function(obj) {
var fn = this;
// 捕获所有 curried 参数
var curried = [].slice.call( arguments, 1 );
var bound = function() {
return fn.apply(
(!this || this === (window || global)) ?
obj : this
curried.concat.apply( curried, arguments )
);
};
bound.prototype = Object.create( fn.prototype );
return bound;
};
将时间戳转换成时间描述
function getTimeDesc(time) {
var
_n = 12 * 30 * 24 * 60 * 60 * 1000,
_y = 30 * 24 * 60 * 60 * 1000,
_d = 24 * 60 * 60 * 1000,
_h = 60 * 60 * 1000,
_m = 60 * 1000,
_s = 1000,
n, y, d, h, m, s, value;
n = parseInt(time > _n ? time / _n : 0);
n = n ? (n + '年') : '';
time = time % _n;
y = parseInt(time > _y ? time / _y : 0);
y = y ? (y + '月') : '';
time = time % _y;
d = parseInt(time > _d ? time / _d : 0);
d = d ? (d + '天') : '';
time = time % _d;
h = parseInt(time > _h ? time / _h : 0);
h = h ? (h + '时') : '';
time = time % _h;
m = parseInt(time > _m ? time / _m : 0);
m = m ? (m + '分') : '';
time = time % _m;
s = parseInt(time > _s ? time / _s : 0);
s = s + '秒';
value = n + y + d + h + m + s;
console.log(value);
return value;
}
toFixed 精度修复
Number.prototype.toFixed = function (n) {
if (n > 20 || n < 0) {
throw new RangeError('toFixed() digits argument must be between 0 and 20');
}
const number = this;
if (isNaN(number) || number >= Math.pow(10, 21)) {
return number.toString();
}
if (typeof (n) == 'undefined' || n == 0) {
return (Math.round(number)).toString();
}
let result = number.toString();
const arr = result.split('.');
// 整数的情况
if (arr.length < 2) {
result += '.';
for (let i = 0; i < n; i += 1) {
result += '0';
}
return result;
}
const integer = arr[0];
const decimal = arr[1];
if (decimal.length == n) {
return result;
}
if (decimal.length < n) {
for (let i = 0; i < n - decimal.length; i += 1) {
result += '0';
}
return result;
}
result = integer + '.' + decimal.substr(0, n);
const last = decimal.substr(n, 1);
// 四舍五入,转换为整数再处理,避免浮点数精度的损失
if (parseInt(last, 10) >= 5) {
const x = Math.pow(10, n);
result = (Math.round((parseFloat(result) * x)) + 1) / x;
result = result.toFixed(n);
}
return result;
};
js 精度运算
var floatObj = function() {
// 判断obj是否为一个整数
function isInteger(obj) {
return Math.floor(obj) === obj
}
/*
* 将一个浮点数转成整数,返回整数和倍数。如 3.14 >> 314,倍数是 100
* @param floatNum {number} 小数
* @return {object}
* {times:100, num: 314}
*/
function toInteger(floatNum) {
var ret = {times: 1, num: 0}
var isNegative = floatNum < 0
if (isInteger(floatNum)) {
ret.num = floatNum
return ret
}
var strfi = floatNum + ''
var dotPos = strfi.indexOf('.')
var len = strfi.substr(dotPos+1).length
var times = Math.pow(10, len)
var intNum = parseInt(Math.abs(floatNum) * times + 0.5, 10)
ret.times = times
if (isNegative) {
intNum = -intNum
}
ret.num = intNum
return ret
}
/*
* 核心方法,实现加减乘除运算,确保不丢失精度
* 思路:把小数放大为整数(乘),进行算术运算,再缩小为小数(除)
*
* @param a {number} 运算数1
* @param b {number} 运算数2
* @param digits {number} 精度,保留的小数点数,比如 2, 即保留为两位小数
* @param op {string} 运算类型,有加减乘除(add/subtract/multiply/divide)
*
*/
function operation(a, b, digits, op) {
var o1 = toInteger(a)
var o2 = toInteger(b)
var n1 = o1.num
var n2 = o2.num
var t1 = o1.times
var t2 = o2.times
var max = t1 > t2 ? t1 : t2
var result = null
switch (op) {
case 'add':
if (t1 === t2) {
// 两个小数位数相同
result = n1 + n2
} else if (t1 > t2) {
// o1 小数位 大于 o2
result = n1 + n2 * (t1 / t2)
} else {
// o1 小数位 小于 o2
result = n1 * (t2 / t1) + n2
}
return (result / max).toFixed(digits);
case 'subtract':
if (t1 === t2) {
result = n1 - n2
} else if (t1 > t2) {
result = n1 - n2 * (t1 / t2)
} else {
result = n1 * (t2 / t1) - n2
}
return (result / max).toFixed(digits);
case 'multiply':
result = (n1 * n2) / (t1 * t2)
return result.toFixed(digits);
case 'divide':
result = (n1 / n2) * (t2 / t1)
return result.toFixed(digits);
}
}
// 加
function add(a, b, digits) {
let value = operation(a, b, digits, "add");
return value == NaN || value == Infinity ? 0 : value;
}
// 减
function subtract(a, b, digits) {
let value = operation(a, b, digits, "subtract");
return value == NaN || value == Infinity ? 0 : value;
}
// 乘
function multiply(a, b, digits) {
let value = operation(a, b, digits, "multiply");
return value == NaN || value == Infinity ? 0 : value;
}
// 除
function divide(a, b, digits) {
let value = operation(a, b, digits, "divide");
return value == NaN || value == Infinity ? 0 : value;
}
return { add, subtract, multiply, divide };
}();
js 滚轮绑定
EventTarget.prototype.onMousewheel = function (fn, capture) {
if (document.mozFullScreen !== undefined) {
type = "DOMMouseScroll";
} else {
type = "mousewheel";
}
this.addEventListener(type, function (event) {
event.delta = (event.wheelDelta) ? event.wheelDelta / 120 : -(event.detail || 0) / 3;
fn.call(this, event);
}, capture || false);
}
js 点击下载
function browserDownload (url) {
var save_link = document.createElementNS("http://www.w3.org/1999/xhtml", "a");
save_link.href = url;
save_link.download = name;
var ev = document.createEvent("MouseEvents");
ev.initMouseEvent(
"click",
true,
false,
window,
0,
0,
0,
0,
0,
false,
false,
false,
false,
0,
null
);
save_link.dispatchEvent(ev);
}
获取区间随机数
function random(n, m){
var random = Math.floor(Math.random()*(m-n+1)+n);
return random;
}
获取梯度随机数
function step_random(min, max, step) {
var newMax = max / step;
var randomNum = Math.floor(Math.random() * (newMax - min + 1) + min)
var stepNum = randomNum * step
return stepNum;
}
数据分组
function groupBy(array, valueKey) {
let groups = {};
let newArray = [];
array.forEach(function(o) {
groups[valueKey] = groups[group] || [];
groups[valueKey].push(o);
});
for(const key in groups) {
newArray = newArray.concat(groups[key]);
}
return newArray;
};
获取查询参数
// 方法1
function getQueryObject() {
const search = window.location.href.split('?')[1]
if (!search) {
return {}
}
return JSON.parse(
'{"' +
decodeURIComponent(search)
.replace(/"/g, '\\"')
.replace(/&/g, '","')
.replace(/=/g, '":"')
.replace(/\+/g, ' ') +
'"}'
)
}
// 方法2
function getQueryObject(url) {
url = url == null ? window.location.href : url;
const search = url.substring(url.lastIndexOf("?") + 1);
const obj = {};
const reg = /([^?&=]+)=([^?&=]*)/g;
search.replace(reg, (rs, $1, $2) => {
const name = decodeURIComponent($1);
let val = decodeURIComponent($2);
val = String(val);
obj[name] = val;
return rs;
});
return obj;
}