[翻译]High Performance JavaScript(021)
Splitting Up Tasks 分解任务
What we typically think of as one task can often be broken down into a series of subtasks. If a single function is taking too long to execute, check to see whether it can be broken down into a series of smaller functions that complete in smaller amounts of time. This is often as simple as considering a single line of code as an atomic task, even though multiple lines of code typically can be grouped together into a single task. Some functions are already easily broken down based on the other functions they call. For example:
我们通常将一个任务分解成一系列子任务。如果一个函数运行时间太长，那么查看它是否可以分解成一系列能够短时间完成的较小的函数。可将一行代码简单地看作一个原子任务，多行代码组合在一起构成一个独立任务。某些函数可基于函数调用进行拆分。例如：
function saveDocument(id){
//save the document
openDocument(id)
writeText(id);
closeDocument(id);
//update the UI to indicate success
updateUI(id);
}
If this function is taking too long, it can easily be split up into a series of smaller steps by breaking out the individual methods into separate timers. You can accomplish this by adding each function into an array and then using a pattern similar to the array-processing pattern from the previous section:
如果函数运行时间太长，它可以拆分成一系列更小的步骤，把独立方法放在定时器中调用。你可以将每个函数都放入一个数组，然后使用前一节中提到的数组处理模式：
function saveDocument(id){
var tasks = [openDocument, writeText, closeDocument, updateUI];
setTimeout(function(){
//execute the next task
var task = tasks.shift();
task(id);
//determine if there's more
if (tasks.length > 0){
setTimeout(arguments.callee, 25);
}
}, 25);
}
相关文档：
JavaScript事件大全
click() 对象.click() 使对象被点击。
closed 对象.closed 对象窗口是否已关闭true/false
clearTimeout(对象) 清除已设置的setTimeout对象
clearInterval(对象) 清除已设置的setInterval对象
confirm("提示信息") 弹出确认框，确定返回true取消返回false
cursor:样式 更改鼠标样� ......
隐藏成员变量
在函数体内定义的变量为局部变量，离开函数就挂掉了
在函数体内使用this.成员变量名，则为window对象级变量，即全局变量
故需要这样隐藏成员变量，向外只暴露get、set函数
function testClass(name){
var _firstname=name;
return {
getname : function() {
return _fir ......
Recursion Patterns 递归模式
When you run into a call stack size limit, your first step should be to identify any instances of recursion in the code. To that end, there are two recursive patterns to be aware of. The first is the straightforward recursive pattern represented ......
Yielding with Timers 用定时器让出时间片
Despite your best efforts, there will be times when a JavaScript task cannot be completed in 100 milliseconds or less because of its complexity. In these cases, it's ideal to yield control of the UI thread so that UI updates may occur ......
