javascript - Using Custom Methods with Custom Objects -

javascript - Using Custom Methods with Custom Objects -

i began working custom objects along custom methods in javascript. practice wrote little script compare 2 involvement rates. @ first thought programme worked, although sure, used document.write(john_interest_value), , received nan alert. using custom methods correctly? can identify problem? thanks.

function simpleinterest (principal,time1,rate) { this.principal = principal; this.time1 = time1; this.rate = rate; this.interest = calculate_interest; } function calculate_interest(principal,time1,rate) { var si; var si = (principal*rate*time1)/100; homecoming si; } var tom_interest = new simpleinterest(1000,3,.08); var john_interest = new simpleinterest(2000,3,.04); var tom_interest_value = tom_interest.interest(); var john_interest_value = john_interest.interest(); window.alert (john_interest_value); if (tom_interest_value > john_interest_value) { document.write("tom's involvement earned more of john's"); } else if (tom_interest_value < john_interest_value){ document.write("john's involvement earned more of tom's"); } else { document.write("tom , john earn equal interest"); }

undefined*undefined equals nan

given way chose phone call below:

var tom_interest_value = tom_interest.interest(); var john_interest_value = john_interest.interest();

the variables within of function calculate_interest undefined. so, have written need

var tom_interest_value = tom_interest.interest(tom_interest.principal, tom_interest.time1, tom_interest.rate);

as can see, typing tedious. want remove parameters calculate_interest , instead reference objects variables below

function calculate_interest() { var si = (this.principal*this.rate*this.time1)/100; homecoming si; }

javascript object methods