Simple Javascript If Statement not Working in ASP.NET MVC view

Question

There might be something obvious I'm missing, but I can't seem to make my Javascript evaluate to 'true' and fire the event I want (setting a checkbox to ticked if the value is true/a string equivalent of true).

Code as follows:

window.onload = function () {
        alert("let's go!");
        var enabledVal = TempData["enabled"];

        if (enabledVal == "checked") {
            alert("made it here");
            document.getElementById("eCheck").checked = true;
        }

    }

I know the onload function is being reached because the alert fires. The TempData["enabled"] is set in the controller as follows:

//returns True/False
            string enabledVal = (from person in testTechObj.People
                                 where person.PersonId.Equals(id)
                                 select person.IsEnabled).SingleOrDefault().ToString();

            if (enabledVal == "True")
            {
                enabledVal = "checked";
            }

... 
//pass enabled/authorised values
            TempData["enabled"] = enabledVal;

I tried checking for both a boolean and a string, but the If statement doesn't evaluate in either case. I know TempData["enabled"] is set to what I'd expect (either "checked" or "True") as I tried writing it out to the screen with @TempData["enabled"] and the values I expected appeared.

Is there something obvious I'm missing?

EDIT: Browser output (third bit of text from the top is @TempData["enabled"] [ enter image description here ]1

It looks like you're mixing server-side code and client-side code. What is the resulting client-side code in the browser? It's probably a syntax error and it throwing an error on the browser's debugging console. — David
– David, Commented May 10, 2017 at 19:51
Is your LINQ query really going to return "True" (a string)? Or, will it return True (a Boolean)? — Scott Marcus
– Scott Marcus, Commented May 10, 2017 at 19:53
it should return "True" a string given that the conversion is used and the variable is a string itself. Part of the reason I converted 'true' into 'checked' was concern that that was what was tripping the browser up. As for server side, just found this in the debugger: 'Uncaught ReferenceError: TempData is not defined at window.onload' — peanut
– peanut, Commented May 10, 2017 at 19:58

Majid Parvin · Accepted Answer · 2017-05-10 19:56:48Z

2

Change TempData to ViewData and onload function to this:

window.onload = function () {
    alert("let's go!");
    var enabledVal = '@ViewData["enabled"]';

    if (enabledVal == "checked") {
        alert("made it here");
        document.getElementById("eCheck").checked = true;
    }

}

answered May 10, 2017 at 19:56

Majid Parvin

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4 Comments

Hans Keﬆing Over a year ago

The important part: the @ which evaluates that "ViewData" server-side and injects it's value into the javascript.

peanut Over a year ago

thanks, that fixed it! it looks as though TempData and ViewData persist differently within the context of views/on load functions

peanut Over a year ago

it looks like the ' ' around the ViewData are important too?

Majid Parvin Over a year ago

yeah, Both of @ and '' are important, @ render your server-side value and '' make a JavaScript string value for you.

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