1. 获取指定Cookie的方法
function getCookie(cookieName){
var cookieValue="";
if (document.cookie && document.cookie != '') {
var cookies = document.cookie.split(';');
for (var i = 0; i < cookies.length; i++) {
var cookie = cookies[i];
var arr= cookie.split('=');
if (arr[0].replace(" ",'') == cookieName) {
cookieValue = arr[1];
break;
}
};
return cookieValue;
};
}
2. 获取当前元素字符串的方法
function nodeToString (node) {
var tempNode = document.createElement("div");
tempNode.appendChild(node.cloneNode(true));
var str = tempNode.innerHTML;
tempNode = node = null;
return str;
}
3. 获取URL指定参数的方法
function getQueryParameter(parameter) {
var query = window.location.search.substring(1);
var arr = query.split("&");
for (var i = 0; i < arr.length; i++) {
var obj = arr[i].split("=");
if (obj[0] == parameter) {
return obj[1];
}
}
return (false);
}
4. 将对象转为URL参数
function urlEncode(param, key, encode) {
if (param == null) {
return ''
};
var paramStr = '';
var t = typeof (param);
if (t == 'string' || t == 'number' || t == 'boolean') {
paramStr += '&' + key + '=' + ((encode == null || encode) ? encodeURIComponent(param) : param);
} else {
for (var i in param) {
var k = key == null ? i : key + (param instanceof Array ? '[' + i + ']' : '.' + i)
paramStr += urlEncode(param[i], k, encode)
}
}
return paramStr;
}
5. 绑定事件的方法,适用于各个浏览器
function addBind(obj, eventType, callBack) {
if (obj.addEventListener) {
obj.addEventListener(eventType, callBack, false);
}else if (window.attachEvent) {
obj.attachEvent('on' + eventType, callBack);
}else {
obj['on' + eventType] = callBack;
}
};
addBind(document, 'click', bodyClick);
6. 移除事件的方法,适用于各个浏览器
function moveBind (objId, eventType, callBack) {
var obj = document.getElementById(objId);
if (obj.removeEventListener) {
obj.removeEventListener(eventType, callBack, false);
} else if (window.detachEvent) {
obj.detachEvent('on' + eventType, callBack);
} else {
obj['on' + eventType] = null;
}
}
7. 清空加载到顶部的JS引用
function clearHeadJs (src) {
var js = document.getElementsByTagName('head')[0].children;
var obj = null;
for (var i = 0; i < js.length; i++) {
if (js[i].tagName.toLowerCase() == "SCRIPT" && js[i].attributes['src'].value.indexOf(src) > 0) {
obj = js[i];
break;
}
}
document.getElementsByTagName('head')[0].removeChild(obj);
};
8. 防抖函数
原理: 在事件被触发n秒后再执行回调,如果在这n秒内又被触发,则重新计时。
适用场景:
1. 按钮提交场景:防止多次提交按钮,只执行最后提交的一次;
2. 服务端验证场景:表单验证需要服务端配合,只执行一段连续的输入事件的最后一次;
3. 搜索联想词场景;
代码:
const debounce = (fn,delay)=>{
let timer = null;
return (...args)=>{
clearTimeout(timer);
timer = setTimeout(()=>{
fn.apply(this,args)
},delay)
}
}
示例:
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>防抖函数</title>
</head>
<body>
<input type="text" class="int" onkeydown="down()">
<script>
function down() {
debounce(() => {
console.log('打印输出')
}, 2000)()
}
const debounce = (fn, delay) => {
let timer = null;
return (...args) => {
clearTimeout(timer);
timer = setTimeout(() => {
fn.apply(this, args)
}, delay)
}
}
</script>
</body>
</html>
9. 节流函数
原理: 规定在一单位时间内。只能触发一次函数。如果这个单位时间内触发多次函数,只有一次生效。
适用场景:
1. 拖拽场景:固定时间只执行一次,防止超高频次触发位置变动;
2. 缩放场景:监控浏览器resize;
3. 动画场景:避免短时间内多次触发动画引起的性能问题。
代码:
const throttle = (fn, delay = 500) => {
let flag = true;
return (...args) => {
if (!flag) return;
flag = false;
setTimeout(() => {
fn.apply(this, args)
}, delay);
}
}
实例:
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>节流函数</title>
</head>
<body>
<script>
// 节流函数
const throttle = (fn, delay = 30000) => {
let flag = true;
return (...args) => {
if (!flag) return;
flag = false;
setTimeout(() => {
fn.apply(this, args)
}, delay);
}
}
// 浏览器窗口缩放
window.onresize = function () {
throttle(() => {
console.log("打印输出")
})()
}
</script>
</body>
</html>