JS(2008-02-27)

 /*************************************Functions as Objects******************************/
 //define a Function object
 var funObj = new Function("alert('aaa');");
 funObj();
 
 //assign to another variable
 var funObj2 = funObj;
 funObj2();

 /*
  * define a Function object with some parameters
  * Form:var functionName = new Function("argument 1",..."argument n", "statements for function body");
  * Note:The main advantage of declaring a function using the new operator is that a script can create a function after a document loads.
  */
  var funObjWithParam = new Function("msg", "alert('aaaa' + msg);");

  funObjWithParam('message');

  /*************************Function Literals and Anonymous Functions*******************/
  //simple use of a function literal
  var literObj = function(name) {alert(name);};

  literObj('bbb');

  //Their primary use is when creating methods for user-defined objects.
  //why not just use the following new-style syntax in the constructor function???
  //Answer:it might use substantially more memory, as new function objects are created every time you create a new object.
  function simpleRoot(name) {
  this.name = name;
  this.sayHi = function() {alert('Hi my name is '+this.name);};
  this.sayAnything = function (msg) { alert(this.name+' says '+msg); };
  this.sayHi2 = sayHi2;

  function sayHi2() {
   alert('Hi my name is '+this.name + "from sayHi2!");
  }
  }

  var fun = new simpleRoot('simpleRootName');

  alert(fun.name);
  fun.sayHi();
  fun.sayAnything('message');
  fun.sayHi2();

  /*
  anonymous function.
  var myArray = [2, 4, 2, 17, 50, 8];
myArray.sort( function(x, y)
              {
               // function statements to do sort
              }
             );
  */

/****************************************Static Variables*************************************/
/*
 function doSum(x, y)              
{
    doSum.totalSum = doSum.totalSum + x + y;    // update the running sum
    return(doSum.totalSum);                     // return the current sum
}

// Define a static variable to hold the running sum over all calls
doSum.totalSum = 0;

document.write("First Call = "+doSum(5,10)+"<<br />>");
document.write("Second Call = "+doSum(5,10)+"<<br />>");
document.write("Third Call = "+doSum(100,100)+"<<br />>");
*/

/***************************************Advanced Parameter Passing****************************/
//read-only length property that indicates the number of parameters the function accepts
//可以接受参数的个数
function paraPass(a, b, c) {}
function paraPass2() {}
alert(paraPass.length);
alert(paraPass2.length);

//possibility by examining the arguments[] array associated with a particular function
//实际传入参数的个数
function paraPass3(a, b, c) {
 alert(paraPass3.arguments.length);
}
paraPass3('a');

/*****************************************Using Functions***********************************/
//tips
//1.Define All Functions for a Script First.
//2.Name Functions Well.
//3.Consider Using Linked .js Files for Functions, But Be Cautious.
//4.Use Explicit Return Statements.
//5.Check Arguments Carefully.
//6.Comment Your Functions.

转载于:https://www.cnblogs.com/tongzhiyong/archive/2008/02/27/1084075.html