如何将 Javascript 中的字符串变量放在一起？ 它只是说“对象未定义”

Question

I have tried for so long to get this code to work. I'm programming a little game when you need to be fast, so I made a stopwatch. But the stopwatch just doesn't want to work. Instead of the seconds the stopwatch is showing Object Undefined and I don't know why. This is the code i'm using:

var stopwatchFrame = 0;
var stopwatchSeconds = 0;
var stopwatchSecondsString = "Nothing";

    stopwatchFrame+=1;
    stopwatchSeconds = floor(stopwatchFrame/updatesPerSecond);
    stopwatchSecondsString = toString(stopwatchSeconds);
    var = "Total time: " + stopwatchSecondsString + " seconds";

I'm using a simple website called Koda.nu , it's a Swedish website for young to learn programming in JS. Some functions is coming from their built in source. I'm new to programming so that's why.

Answer 1

You are missing a variable name where you have a value of "Total time: " + stopwatchSecondsString + " seconds"; It should be:

var totalTime = "Total time: " + stopwatchSecondsString + " seconds";

Also read what @Jaromanda X wrote in the comments section. It should be like this:

stopwatchSeconds = Math.floor (stopwatchFrame/updatesPerSecond); stopwatchSecondsString = stopwatchSeconds.toString() ;

We don't have an access to your updatesPerSecond variable so that would throw an error as well. If declared, your code would work like this:

var stopwatchFrame = 0;
var stopwatchSeconds = 0;
var stopwatchSecondsString = "Nothing";
var updatesPerSecond = 0;

stopwatchFrame += 1;
stopwatchSeconds = Math.floor(stopwatchFrame / updatesPerSecond);
stopwatchSecondsString = stopwatchSeconds.toString();
var totalTime = "Total time: " + stopwatchSecondsString + " seconds";

Answer 2

You dont have a variable name in the last line, and if this is all your code, then you dont initialize updatesPerSecond, meaning you dont have a line like

var updatesPerSecond = somenumberhere

If you name your last variable and initialize updatesPerSecond then you should be fine.

However I dont know anything about this website, but I quess it's old. Here is some advice.

You need to tell javascript, that floor is a function from Math so use Math.floor , maybe it works in this website like you did, but keep in mind that you should use it otherwise.

toString() doesnt work like that. Again I dont know if they are using some different methods, but normal js toString() works like number .toString() and u can pass the radix as a parameter, meaning the base of the number representation (2 for binary, 16 for hexadecimal etc.) but this is optional, default is 10 for decimal.

Dont use var as a declaration. Use let instead, if the variable will change, and use const if it wont. In your case you should use let everywhere.

Other thing is that you can use the ++ operator to increment a value by 1, so instead of stopwatchFrame+= 1 just use stopwatchFrame++

And last you shouldn't initialize your default string value as "Nothing", it should be "", an empty string or undefined or null.

I hope this helps, have a good day!