javascript - If statement is not working properly - Stack Overflow

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I'm trying to change the condition in which data is written to a table. I noticed a strange result when trying to change this: it seems WriteToTable function would runno matter what if condition I subjected it to. To test this I did the following:

var TestThis=0;

if (TestThis=1000){
WriteToTable(iPlaceDisplayNum, place.name, place.rating, xScoreFinal, iProspect, place.url, place.formatted_phone_number);
alert ('This alert should not be displaying.');
}

The function will still execute and the alert will be still be displayed when the script runs. I'm not sure why?

Here's the rest of the function, the problem is towards the bottom:

function printme(place, status) {
    if (status == google.maps.places.PlacesServiceStatus.OK) {


        if (typeof place.reviews !== 'undefined') {

            var xScore = 0;
            var xGlobal = 0;

            for (var i = 0; i < place.reviews.length; i++) {

                reviews = place.reviews[i];


                for (var x = 0; x < reviews.aspects.length; x++) {
                    aspectr = reviews.aspects[x];
                    xScore += aspectr.rating;
                    xGlobal++;
                }
            }
            var xScoreFinal = (xScore / xGlobal);

        }

        if (typeof xScoreFinal !== 'undefined') {
            iPlaceDisplayNum++;

            var iProspect;
            if (xScoreFinal < 2.3) {
                iProspect = 'Yes';
            }


     //Not sure what's going on here
     var TestThis=0;

            if (TestThis=1000){
        WriteToTable(iPlaceDisplayNum, place.name, place.rating, xScoreFinal, iProspect, place.url, place.formatted_phone_number);
        alert ('This alert should not be displaying.');
        }

        }
    }
}

I'm trying to change the condition in which data is written to a table. I noticed a strange result when trying to change this: it seems WriteToTable function would runno matter what if condition I subjected it to. To test this I did the following:

var TestThis=0;

if (TestThis=1000){
WriteToTable(iPlaceDisplayNum, place.name, place.rating, xScoreFinal, iProspect, place.url, place.formatted_phone_number);
alert ('This alert should not be displaying.');
}

The function will still execute and the alert will be still be displayed when the script runs. I'm not sure why?

Here's the rest of the function, the problem is towards the bottom:

function printme(place, status) {
    if (status == google.maps.places.PlacesServiceStatus.OK) {


        if (typeof place.reviews !== 'undefined') {

            var xScore = 0;
            var xGlobal = 0;

            for (var i = 0; i < place.reviews.length; i++) {

                reviews = place.reviews[i];


                for (var x = 0; x < reviews.aspects.length; x++) {
                    aspectr = reviews.aspects[x];
                    xScore += aspectr.rating;
                    xGlobal++;
                }
            }
            var xScoreFinal = (xScore / xGlobal);

        }

        if (typeof xScoreFinal !== 'undefined') {
            iPlaceDisplayNum++;

            var iProspect;
            if (xScoreFinal < 2.3) {
                iProspect = 'Yes';
            }


     //Not sure what's going on here
     var TestThis=0;

            if (TestThis=1000){
        WriteToTable(iPlaceDisplayNum, place.name, place.rating, xScoreFinal, iProspect, place.url, place.formatted_phone_number);
        alert ('This alert should not be displaying.');
        }

        }
    }
}

• javascript

Share Improve this question Follow edited Aug 30, 2013 at 18:54 Mark Meyer 3,74333 gold badges2525 silver badges3535 bronze badges asked Aug 30, 2013 at 18:43 dlofrodlohdlofrodloh 1,74433 gold badges2525 silver badges4848 bronze badges 2

• 1 Just noting in your "test" you had an = instead of ==. But that may just be a transposition error? – Doug Morrow Commented Aug 30, 2013 at 18:45
• 1 You would not believe how many people are having exactly the same issue. – Felix Kling Commented Aug 30, 2013 at 19:12

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5 Answers 5

Sorted by: Reset to default 7

You are assigning a value to your variable in your if condition check. Your TestThis variable is being assigned value 1000, which will be true after being converted to boolean by JavaScript. That's why your function is being always executed. You can read more about the automatic type conversion here.

Now to fix your code, change this -

if (TestThis=1000)

to this -

if (TestThis == 1000)

or if you don't want automatic type conversion -

if (TestThis === 1000)

Sometimes people like to reverse the values in the parison, in the following way -

if (1000 === TestThis)

This is called a Yoda Condition (yeah, named after the Grand Jedi Master Yoda) . The benefit is that in case someone mistakenly puts only a single equal, it will result in an error as you cannot assign anything to a constant. I have never used it personally though (and probably never will because I find it rather unconventional).

JavaScript allows you to assign a value in a conditional, so this TestThis=1000 results to 1000 and in a conditional statement positive numbers (actually anything not 0) result to an evaluation to true.

To make it a conditional, you should do TestThis===1000 (and you should almost always use the === over the == as the === forces an actual parison of the two and doesn't try to convert one part of the conditional to equal the other.)

You can also do 1000 === TestThis (or conversly 1000 == TestThis) Some people say this is bad coding, because it's difficult to read. I'll leave that up to you to decide, but this absolutely won't allow you to accidentally assign a value in the conditional because you can't assign a value to 1000.

In the if statement, you're setting TestThis to 1000, rather than paring it to 1000. The = operator returns the value that was set, which evaluates to true because it is not undefined, 0, or null. You simply need to use the == operator.

if(TestThis == 1000)

if (TestThis == 1000)

Change like this.

For paring equality in if you must have ==

Change:

if (TestThis=1000)

To:

if (TestThis==1000)

You're actually assigning to TestThis which will return true and execute the conditional block.

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