js小技巧

1.判断当前js环境是否为严格模式

//定义并调用一个函数来确定当前脚本运行时是否为严格模式
var strict = (function() { return !this; })();

 2.检测一个对象是否是真正的函数对象

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

3.低版本不兼容e.preventDefault()和e.target

//获取事件对象
var getEvent = function (event) {
    //标准浏览器返回event, IE下window. event
    return event || window. event ; 
}
//获取元素!
var getTarget = function (event) {
    var event = getEvent (event) ;
    //标准浏览器下event.target, IE下event.srcElement
    return event.target || event.srcElement;
}
//阻止默认行为
var preventDefault = function (event) {
    var event = getEvent (event) ;
    //标准浏览器
    if (event.preventDefault) {
        event.preventDefault () ;
    // IE浏览器
    }else {
        event. returnValue = false;
    }
}