Sometime, use can rewrite the toString , valueOf method to make those function more useful:
For exmaple, we can make valueOf() function to calcualte the sum, and then use toString method to display the information of the object we create.
var Tornado = function(category, affectedAreas, windGust){
this.category = category;
this.affectedAreas = affectedAreas;
this.windGust = windGust;
};var cities = [["Kansas City", 46310],["Topeka", 127939],["Lenexa", 49398]];
var twister = new Tornado("F5", cities, 220);
cities.push(["Olathe", 130045]);
twister.toString();Tornado.prototype.toString = function(){
var list = "";
for(var i = 0; i< this.affectedAreas.length; i++){
if(i < this.affectedAreas.length-1){
list = list + this.affectedAreas[i][0] + ", ";
}else{
list = list + "and "+ this.affectedAreas[i][0];
}
}
return "This tornado has been classified as an " + this.category+
", with wind gusts up to "+ this.windGust+ "mph. Affected areas are:"+
list+", potentially affecting a population of "+ this.valueOf() + ".";
};Tornado.prototype.valueOf = function(){ var sum = 0;
for(var i = 0; i < this.affectedAreas.length; i++){
sum += this.affectedAreas[i][1];
}
return sum;
}Object.prototype.findOwnProperty = function(propName){
var currentObject = this;
while(currentObject !== null){
if(currentObject.hasOwnProperty(propName)){
return currentObject;
}else{
currentObject = currentObject.__proto__;
}
}
return "No property found!";
}
twister.findOwnProperty("valueOf");