When should you use try/catch in JavaScript?

Question

When I'm developing normal web application with JavaScript, the try/catch statement is not needed usually. There's no checked exception, File IO or database connection in JavaScript.

Is try/catch statement useful in JavaScript? When can I use it?

Answer 1

try...catch blocks are generally encourages to be used less, and this doesn't depend on the language you use.

The main reason for this is the cost of catch blocks. Also another reason is that, when you wrap many statements with a single try...catch block, in catch block you can't be sure what was exactly the main problem.

It's better to use techniques like input validation or if...else blocks to reduce the probability of an exception (error) to happen. For example, when you want to work with a number which is taken from user, instead of using try...catch, you can use:

if (isNaN(numberVariable)) {     alert('you should enter a valid number'); } 

Answer 2

One scenario I find try/catch/finally useful is with deeply nested objects where a null can pop up at any level. for example, consider this:

var something = one.two.three.four.five; 

to perform this "get" with 100% safety one would have to write a bit of verbose code:

if(one && one.two && one.two.three && one.two.three.four)    something = one.two.three.four.five; 

Now imagine the variable names are realistic and longer and you quickly get a very ugly code if statement.

I tend to use try/catch/finally to simplify this when I don't care about any "else" scenarios and just want the object or not:

var something; try { something = one.two.three.four.five; } catch { something = "default"; } finally { doSomething(something); }