如何在JavaScript的一行中无错误地调用可能不存在的方法？

Question

I was writing a program that uses javascript and creates inheritance in a way.

If the user types in:

x.isSingleLine()

and it does not exist, it crashes Javascript. I was hoping there was a way to do something like:

x.isSingleLine() || "Doesnt Exist";

to in a way have it do a soft error or some sort of alert. I didnt want to have to encapsulate the object in a try-catch block.

Is there a way this can be accomplished?

In the statement: x.isSingleLine() || "Doesnt Exist"; it will crash and not do the OR part, so this is not the answer apparently.

Answer 1

How about that?

  x.isSingleLine ? x.isSingleLine() : console.log("Doesnt Exist");

Edit: As suggested by @FelixKling if there's a chance that isSingleLine exists but is not a function you should instead use:

(x.isSingleLine && x.isSingleLine instanceof Function) ? x.isSingleLine() : console.log("Doesnt Exist");

Answer 2

您需要在调用之前检查它是否存在。

var result = x.isSingleLine ? x.isSingleLine() : "Doesn't Exist";

Answer 3

As far as I know from the top of my head, you can use a try-catch block for that:

try {
    x.isSingleLine();
} catch (e) {
    // Something happened
    alert("isSingleLine didn't quite work out.");
}

Play around with it in this fiddle

Update I now noticed that you don't want to encapsulate in a try-catch block. Using a try-catch block though can even handle errors inside the isSingleLine() method as shown in the updated fiddle .

Answer 4

(x.isSingleLine || function(){
    console.log("Doesn't Exist");
})()