js doesn't execute 'else' statement

Question

I have an if-else statement in JavaScript which returns false, but doesn't execute the code inside 'else'.

part of the script inside the cshtml file:

if (@Session["mission"].ToString() != "1") {
    setInterval(function () { myTimer(ctxPoints, ctxLines); }, 1000 / @ViewBag.rate);  
} else {
    alert("hi");
}

In the debug the '@Session["mission"].ToString() != "1"' statement returns false, but nothing jumps to the screen.

What is @Session["mission"].ToString()? Did you mean toString? — Jack Bashford
– Jack Bashford, Commented May 30, 2019 at 9:06
seems like Razor C# syntax so it is C# .ToString() with uppercase, but you should check the value of @Session["mission"].ToString() to make sure it is what you expect — Slai
– Slai, Commented May 30, 2019 at 9:11
you might need to do a null checking on @Session["mission"] before the if else statement, just to ensure that it is not null — Se0ng11
– Se0ng11, Commented May 30, 2019 at 9:11
It is not null.. the '@Session["mission"].ToString()' returns "2" (string type) and the '@Session["mission"].ToString() == "1"' returns false (bool type) — michele abr
– michele abr, Commented May 30, 2019 at 9:14

JotaBe · Accepted Answer · 2019-05-30 09:21:37Z

You should open your web browser Developer console and see the real script which reaches the browser.

The Razor parts, @Session["mission"].ToString() doesn't exists in the browser script, because they are evaluated in the server, before sending them to the browser. So it makes no sense to try @Session["mission"].ToString() != "1" this in the console. In the browser you will get something like: if (1 != "1") or even like if ( != "1") which would provoke an error.

JavaScript does coalescing, so 1 is equal to "1" when you use the comparers == or !=, so you don't need to include the qoutes around the value (unless you get the error mentioned above: in this case, if you included the quotes, you'd get if ("" != "1")).

Coalescing is avoided by using the !== or === which would consider 1 not equal to "1", so, including the quotes doesn't make any difference in this case.

Bùi Đức Khánh · Accepted Answer · 2019-05-30 09:12:19Z

2

I think you should clear Js code and c# code

if ("@Session["mission"].ToString()" != "1")

Session["mission"].ToString() this print string in c#, but you need to encapsulate it in quote to make this value get type string

answered May 30, 2019 at 9:12

Bùi Đức Khánh

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4 Comments

Slai Over a year ago

hmm I can't see how that can be an issue even if it is if (1 != "1") instead of if ("1" != "1"), and I am guessing the quotes inside might need to be escaped

Bùi Đức Khánh Over a year ago

@slai you are right, my answer is only helping him has safer code. Problem must relate to another code problem

JotaBe Over a year ago

Downvoted beacuse the first comment is right. if you want to explain how to write "safer code" you should mention the difference between != vs !== and == vs ===

Bùi Đức Khánh Over a year ago

@JotaBe Yes, I upvoted for your answer because It is detail enough

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