数组求和

function sum(){
    var result=0;
    for(var i=0;i<arguments.length;i++){
        result+=arguments[i];   
    }
    return resulat;                     
}

alert(sum(2,5));

var arr=[2,5];
Array.prototype.sum=function(){
   var result=0;
   for(var i=0;i<this.length;i++){
       result+=this[i]     
    }
    return resulat;   
};
 
alert(arr.sum());