函数作为参数

参数作为方法名，执行方法

 

 

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(operateor, operand1, operand2){

return operateor(operand1, operand2);

}

 

var i = operate(add, operate(add, 2, 3), operate(multiply, 4, 5));

console.log(i);

 

console.log("===============");

 

var operateors = {

add: function(x, y){return x+y},

subtract: function(x,y){returnx-y},

multiply: function(x,y){returnx*y},

divide: function(x,y){returnx/y},

pow:Math.pow

};

 

function operate2(operation, operand1, operand2){

if(typeof operateors[operation] === 'function'){

return operateors[operation](operand1, operand2);

}

}

 

var j = operate2("add", "hello", operate2("add", " ", "world"));

console.log(j);

console.log(operate2("pow", 10, 2));