isset-helper

Isset Helper

A tiny helper method for Javascript, checking a variable for existence.

Since checking variable types and existence always has been painful in Javascript, validation conditions normally are exhausting. This module solves this definitely.

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Installation

$ npm install --save isset-helper
# or
$ yarn add isset-helper

Require

const isset = require('isset-helper');

or if you prefer a more object-oriented usage of this method:

const Util = {
  isset: require('isset-helper')
}

Usage

isset(variable,type) {}
// or
Util.isset(variable,type) {}

variable can be anything. It's value is going to be checked.
type can be a string, class or even left empty.

The algorithm follows the subsequent rules:

1. variable is not null
2. variable is not undefined
3. If type is a string, typeof variable has to match type
4. Otherwise, variable has to match instanceof type
5. If type is "string", variable is not an empty string

Please notice:

• The algorithm always runs the instanceof-check, leaving it out of consideration if the check runs in any error.
• The algorithm doesn't check for the exact value (apart from the empty string case mentioned above), thus false will also be considered valid.

Examples

Form validation

(Example below use jQuery syntax for simplification. It's not required for the helper to work!)

$('#myform').on('submit',function (event) {
  var user = $(this).find('#username').val()
  if(!Util.isset(user,'string')) return false

  var pass = $(this).find('#password').val()
  if(!Util.isset(pass,'string')) return false
})

Constructor validation

class House {...}

class Person {
  constructor(name,age,house) {
    if(Util.isset(name,'string')) {
      this.name = name;
    } else {
      throw new Error('Person constructor is missing required argument: name')
    }

    if(Util.isset(age,'number')) {
      this.age = age;
    } else {
      throw new Error('Person constructor is missing required argument: age')
    }

    if(Util.isset(house,House)) {
      this.house = house;
    } else {
      throw new Error('Person constructor is missing required argument: house')
    }
  }
}