javascript重点笔记

操作符之间的优先级（高到低）：算术操作符 》比较操作符 》逻辑操作符 》"="赋值符号

算术运算符

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" 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比较运算符

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" alt="" />

逻辑运算符
aaarticlea/png;base64,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" alt="" />

数组

1.创建的新数组是空数组，没有值，如输出，则显示undefined。

2.虽然创建数组时，指定了长度，但实际上数组都是变长的，也就是说即使指定了长度为8，仍然可以将元素存储在规定长度以外。

substring() 方法用于提取字符串中介于两个指定下标之间的字符

stringObject.substring(starPos,stopPos)

注意：

1. 返回的内容是从 start开始(包含start位置的字符)到 stop-1 处的所有字符，其长度为 stop 减start。

2. 如果参数 start 与 stop 相等，那么该方法返回的就是一个空串（即长度为 0 的字符串）。

3. 如果 start 比 stop 大，那么该方法在提取子串之前会先交换这两个参数。

substr() 方法从字符串中提取从 startPos位置开始的指定数目的字符串

stringObject.substr(starPos,stopPos)

注意：

如果参数startPos是负数，从字符串的尾部开始算起的位置。也就是说，-1 指字符串中最后一个字符，-2 指倒数第二个字符，以此类推。

如果startPos为负数且绝对值大于字符串长度，startPos为0。

sort()方法使数组中的元素按照一定的顺序排列

arrayObject.sort(方法函数)

参数说明：

1.如果不指定<方法函数>，则按unicode码顺序排列。

2.如果指定<方法函数>，则按<方法函数>所指定的排序方法排序。

注意:

该函数要比较两个值，然后返回一个用于说明这两个值的相对顺序的数字。比较函数应该具有两个参数 a 和 b，其返回值如下：

　　若返回值<=-1，则表示 A 在排序后的序列中出现在 B 之前。

　　若返回值>-1 && <1，则表示 A 和 B 具有相同的排序顺序。

　　若返回值>=1，则表示 A 在排序后的序列中出现在 B 之后。

事件冒泡解释

即事件最开始由最具体的元素（文档中嵌套层次最深的那个结点）接收，然后逐级向上传播至最不具体的那个结点（文档）

事件捕获解释

不太具体的结点应该更早接受到事件，而最具体的结点最后接受到事件。

事件处理程序类别

1.html事件处理程序，直接html中添加事件

<div class="up_out" onclick="alert()">点击</div>

2.DOM0级事件处理程序，id获取元素，绑定事件

document.getElementById('').onclick=function(){}

3.DOM2级事件处理程序，addEventListener()和removeEventListener()，有浏览器兼容问题

document.getElementById('').addEventListener('click',function(){})

4.问题IE6-8:attachEvent()和decachEvent()，参数问题要区分onclick

document.getElementById('').attachEvent('onclick',function(){})

5.跨浏览器  重点：element.onclick===element[onclik]

var eventUtil={
    // 添加句柄
    addHandler:function(element,type,handler){
        if(element.addEventListener){
            element.addEventListener(type,handler,false);
        }else if(element.attachEvent){
            element.attachEvent('on'+type,handler);
        }else{
            element['on'+type]=handler;
        }
     },
     // 删除句柄
     removeHandler:function(element,type,handler){
        if(element.removeEventListener){
             element.removeEventListener(type,handler,false);
        }else if(element.detachEvent){
             element.detachEvent('on'+type,handler);
        }else{
             element['on'+type]=null;
        }
     },
     getEvent:function(event){
　　　　　//IE兼容
        return event?event:window.event;
     },
     getType:function(event){
        return event.type;
     },
     getElement:function(event){
        return event.target || event.srcElement;
     },
     preventDefault:function(event){
        if(event.preventDefault){
              event.preventDefault();
        }else{
              event.returnValue=false;
        }
    },
    stopPropagation:function(event){
        if(event.stopPropagation){
             event.stopPropagation();
        }else{
             event.cancelBubble=true;
        }
    }
  }