CODEWITHSUNDEEP
javascriptif-statementbooleanconditional-statements
LoB
LoB

Reputation: 35

if (true || true || false) statement is true in javascript?

I have this bit of code to protect my page from being iframed. 

window.onload = function(){
 try
  {
   if (window.parent && window.parent.location.hostname !== "app.herokuapp.com"){
      throw new Error();
   }
   catch (e){
   //do something
   }
  }

It works perfectly fine until I try to add more values to compare the hostname with. I want to add my custom domain name. I tried this: 

window.onload = function(){
 try
  {
   if (window.parent && (window.parent.location.hostname !=="app.herokuapp.com" 
   || window.parent.location.hostname !== "www.app.com"
   || window.parent.location.hostname !== "localhost")){
      throw new Error();
   }
   catch (e){
   //do something
   }
  }

This always returns true and therefore throws an error. How can I make this work? Unless the hostname matches these strings, I want to throw an error and it throws an error no matter what. I am new at this and would love some help! Thanks.

Ps. I added "localhost" because I want to be able to test it locally before pushing to heroku.

Upvotes: 1

Views: 1685

Answers (2)

elclanrs
elclanrs

Reputation: 94101

Since there's already a pretty complete answer I would suggest a different approach. When you have long statements like that, I find that working with higher-order functions is easier to read. Think of your condition this way: "Check if the hostname doesn't match any of the given strings". That's how I would like to read the code, everything else is boilerplate:

function not(y) {
  return function(x) {
    return x !== y;
  };
}

var hosts = ['app.herokuapp.com','www.app.com','localhost'];
var parent = window.parent;

if (parent && hosts.some(not(parent.location.hostName))) {
  ...
}

Upvotes: 0

p.s.w.g
p.s.w.g

Reputation: 149000

|| returns evaluates to true if any of the operands evaluate to true. Perhaps you meant to use && instead:

if (window.parent 
    && window.parent.location.hostname !== "app.herokuapp.com" 
    && window.parent.location.hostname !== "www.app.com"
    && window.parent.location.hostname !== "localhost")

Or by De Morgan's Law:

if (window.parent 
    && !(window.parent.location.hostname === "app.herokuapp.com" 
         || window.parent.location.hostname === "www.app.com"
         || window.parent.location.hostname === "localhost"))

This will evaluate to true if all of the operands evaluate to true.

Further Reading

Upvotes: 6

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