Catcher

Functional errors interceptions

Table of contents

• Setup
• Usage
• Examples

Setup

This module can then be installed with yarn:

yarn add @jdes/catcher

Usage

Import module:

/**
 * @type {function}
 */
const Catcher = require('@jdes/catcher');

API

Methods

resolve(fn: function: [, defaults: = undefined]): *

• fn: The function to execute and which can throws an Error.
• direction: The defaults value to return if fn fails

Execute the function fn surrounding with try/catch block.
If all is ok, catcher returns the value returned by fn.

reject(error: Error = new Error())

• error: The error to throw

Throws the error give in arguments.

Examples

Resolves with “fs” package

const fs = require('fs');
const util = require('util');
const Catcher = require('@jdes/catcher');
// Call fs.accessSync which throws an error with unknown path
const filename = './unknown';
const exists = Catcher.resolve(() => fs.accessSync(filename)) ? true : false;
const promisify = util.promisify;
if (exists) {
  promisify(fs.readFile)(filename)
    .then((data) => console.log(data))
    .catch((error) => console.error(error));
}

Resolve with default value

const Catcher = require('@jdes/catcher');
// Check if the argument is equal to "jimmy" (after transform it to lower case).
// If it is not, it throws an Error.
// The Error is catched by the catcher and returns the default value : false
const isJimmy = (name) => {
  if (name.toLowerCase() !== 'jimmmy') {
    throw new Error();
  }
  return true;
};
if (Catcher.resolve(() => isJimmy('Toto'), false)) {
  console.log('Hello Jimmy');
} else {
  console.error('Who are you?');
}

Reject functionally

const Catcher = require('@jdes/catcher');
// Returns true if name equals "jimmy" or throws an Error
const isJimmy = (name) => {
    return name.toLowerCase() === 'jimmy' || Catcher.reject(new Error());
};
try {
  if (isJimmy('Toto')) {
      console.log('Hello Jimmy');
  }
} catch (error) {
    console.error('Who are you?');
}