一些常用的JS函数

//获取元素属性

function getStyle(obj, attr) {

return obj.currentStyle ? obj.currentStyle[attr] : getComputedStyle(obj, 0)[attr];

}

//运动函数

function doMove(obj, attr, speed, target, endFn) {

clearInterval(obj.timer);

speed = parseInt(getStyle(obj, attr)) < target ? speed : -speed;

//alert(speed);

obj.timer = setInterval(function () {

var curPosition = parseInt(getStyle(obj, attr)) + speed;

if (curPosition > target && speed > 0 || curPosition < target && speed < 0)

curPosition = target;

obj.style[attr] = curPosition + 'px';

if (curPosition == target) {

clearInterval(obj.timer);

endFn && endFn();

}     }, 50); }

//抖动函数

//透明度渐变函数

//需找与数组相等的值函数

function arrIndexOf(arr, v) {

for (i = 0; i < arr.length; i++) {

if (arr[i] == v) {

return i; //返回与目标值相等的数组的下标值

}

}

return -1;

}

//getElementByClassName函数

function getElementByClassName(parent, tagName, className) {

var aEls = parent.getElementsByTagName(tagName);

var arr = [];

for (var i = 0; i < aEls.length; i++) {

var arrClassName = aEls[i].className.split(' ');

var _index = arrIndexOf(arrClassName, className);

if (_index != -1) {

arr.push(aEls[i]);

}

}

return arr;

}

//addClass函数

function addClass(obj, className) {

if (obj.className == '') {

//如果原来没有class

obj.className = className;

}

else {

var arrClassName = obj.className.split(' ');

var _index = arrIndexOf(arrClassName, className);

if (_index == -1) {

//如果要添加的class在原来的class中不存在

obj.className += ' ' + className;

}

//如果要添加的class在原来的class中存在,则不需要做任何事

}

}

//removeClass函数

function removeClass(obj, className) {

//如果原来有class

if (obj.className != '') {

var arrClassName = obj.className.split(' ');

var _index = arrIndexOf(arrClassName, className);

if (_index != -1) {

arrClassName.splice(_index, 1);  //删除需要删除的calss

obj.className = arrClassName.join(' '); //然后将arrClassName数组拼接起来

}

}

}

//绑定事件函数

function bind(obj, evname, fn) {

if (obj.addEventListener) {

obj.addEventListener(evname, fn, false);

} else {

obj.attachEvent('on' + evname, function () {

fn.call(obj);             //fn()==fn.call()  call(第一个参数,第二个参数) call函数可以改变函数this的指向,call函数传入的第一个参数就是改变this指向的值,call的第二第三个参数就是原函数的参数

});

}

}

//鼠标在可视区域内的拖拽 不兼容非标准IE

function clientDrag(obj) {

obj.onmousedown = function (ev) {

ev = ev || event;

var ms_b = ev.clientX - obj.offsetLeft;

var ms_t = ev.clientY - obj.offsetTop;

document.onmousemove = function (ev) {

ev = ev || event;

var currX = ev.clientX - ms_b;

var currY = ev.clientY - ms_t;

var Width = document.body.clientWidth || document.documentElement.cilentWidth;

var Height = document.body.clientHeight || document.documentElement.cilentHeight;

if (currX < 0) { currX = 0; }

else if (currX > Width - obj.clientWidth) {

currX = Width - obj.clientWidth;

}

if (currY < 0) { currY = 0; }

else if (currY > Height - obj.clientHeight) {

currY = Height - obj.clientHeight;

}

obj.style.left = currX + 'px';

obj.style.top = currY + 'px';

return false;

}

document.onmouseup = function () {

document.onmousemove = document.onmouseup = null;

}

}

}