javascript定义函数的方法

以下是各种方法的示例代码复制代码代码如下: <html> <head></head> <body> <script type="text/javascript"> /*javascript定义函数(声明函数)可以有三种方法：正常方法、构造函数、函数直接量。*/ /*1.正常方法 function(param){}*/ function print(msg) { document.write(msg,"<br/>"); } /*如果函数不包含return 语句，只执行函数体内语句，并返回undefined*/ /*2.构造函数方法：new Function()*/ var add1=new Function('a','b','return a+b'); /*3.函数直接量法，创建未命名函数，*/ var result = function(x,y){return x+y;}; /*也可以指定函数名*/ var result2 = function fact(x){if(x<1) return 1;else return x*fact(x-1)}; document.write('调用一般的方法：'); print("<hr/>"); print('调用构造函数方法：add1(5,6)'); print(add1(5,6)); print("<hr/>"); print("调用函数直接量法:result(3,4)"); var re =result(3,4); print(re); print("调用函数直接量法:result2(3)"); print(result2(3)); print("<hr/>"); print('函数作为数据使用'); /*函数可以作为数据使用*/ function add(x,y){return x+y;} function subtract(x,y){return x-y;} function multiply(x,y){return x*y;} function divide(x,y){return x/y;} function operate(operator,operand1,operand2) { return operator(operand1,operand2); } //计算(2+3) + (4*5) var i = operate(add,operate(add,2,3),operate(multiply,4,5)); print('(2+3) + (4*5)='+i); print("<hr/>"); //使用函数直接量 var operators = new Object(); operators['add'] = function(x,y){return x+y;} operators['substract'] = function(x,y){return x-y;} operators['multiply'] = function(x,y){return x*y;} operators['divide'] = function(x,y){return x/y;} operators['pow'] = Math.pow; function operate2(op_name,operand1,operand2) { if(operators[op_name] == null) return "unknown operator"; else return operators[op_name](operand1,operand2); } //定义"hello" + "" + "world" var j = operate2("add","hello",operate2("add"," ","world")); var k = operate2("pow",10,2); print(j); print(k); print("<hr/>"); </script> </body> </html> 运行结果为：调用一般的方法： -------------------------------------------------------------------------------- 调用构造函数方法：add1(5,6) 11 -------------------------------------------------------------------------------- 调用函数直接量法:result(3,4) 7 调用函数直接量法:result2(3) 6 -------------------------------------------------------------------------------- 函数作为数据使用 (2+3) + (4*5)=25 -------------------------------------------------------------------------------- hello world 100

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