try-catch-expression

try-catch-expression provides try..catch as expression.

Status

| Category | Status | | ---------------- | --------------------------------------------------------------------------------------------------- | | Version | | | Dependencies | | | Dev dependencies | | | Build | | | License | |

Installation

$ npm install try-catch-expression

Rationale

For handling errors, JavaScript and TypeScript provide the try / catch statement. While it is highly useful, it sometimes makes your code hard to read, e.g. if you want to assign a variable and have a fallback in the catch clause:

let result;

try {
  result = getValue();
} catch {
  result = getDefaultValue();
}

console.log(result);

For this (and other) scenarios it would be helpful it try / catch was also available as an expression, so that you could write your code in a more convenient way:

const result = try {
  return getValue();
} catch {
  return getDefaultValue();
}

console.log(result);

Unfortunately, neither JavaScript nor TypeScript support this. That's what this module adds.

Quick start

First you need to add a reference to try-catch-expression in your application:

const { tryCatch, tryFinally, tryCatchFinally } = require('try-catch-expression');

If you use TypeScript, use the following code instead:

import { tryCatch, tryFinally, tryCatchFinally } from 'try-catch-expression';

To use a simple try / catch, use the tryCatch function and pass a potentially failing function as well as a function that acts as a catch clause. In that function, you may return a value that is then also returned by the surrounding tryCatch function, or re-throw.

const result = tryCatch(
  () => {
    // Try something...
  },
  ex => {
    // Return a default value or re-throw the exception.
  }
);

This means that the variable result will then either contain the return value of the try function, in case it succeeds. If it fails, the value from the catch function is returned. Any error thrown in the catch function will be passed through to the enclosing scope.

Using finally

Besides tryCatch, there are also tryCatchFinally and tryFinally available:

const result = tryCatchFinally(
  () => {
    // Try something...
  },
  ex => {
    // Return a default value or re-throw the exception.
  },
  () => {
    // Clean up.
  }
);

const result = tryFinally(
  () => {
    // Try something...
  },
  () => {
    // Clean up.
  }
);

Note that the return value of the finally function will be discarded, to avoid confusing behavior.

Running quality assurance

To run quality assurance for this module use roboter:

$ npx roboter