Shoehornjs NPM

ShoehornJS

ShoehornJS is a simple and small JavaScript tool for creating type safety. It insures that your variables are being assigned the corrent datatypes and provides a way of improving your error handling for these datatypes.

ShoehornJS can be required for use with NodeJS.

Getting Started

The Initial Call

In the browser Shoehorn is available globally as either shoehorn or shType (in NodeJS it's available as whatever you require it as). shoehorn is a function that accepts an object as its only argument.

var myObject = {
  variableName: String,
  lineNumber: Int,
  fileName: String
};

shoehorn(myObject);

variableName: String

This argument should be a string and will be used in the error message as the name of the variable that you are assigning a value to.

lineNumber: Int

This argument should be a number and will be included in the error message as the line where the error occurs.

fileName: String

This argument should be a String and will be included in the error message as the file where the error occurs.

Note: A normal error stack will still be logged. These options give you the opportunity to make the error log a bit more robust and understandable.

Assigning a Value

shoehorn() returns an object with other functions to be called.

{
  help: function()
  trueType: function(value)
  compareType: function(type1, type2)
  typeError: function(wantedType, value)
  Object: function(value)
  Array: function(value)
  String: function(value)
  Bool: function(value)
  Func: function(value)
  Int: function (value)
  Float: function (value, fixedValue)
}

help: function

This will log to the console a short thank you message and a "TL;DR" of how to use ShoehornJS

trueType: function(value)

This will return a string of the true datatype of a given value, with the first letter of that datatype being capitalized. Normally in JS datatypes returned from typeof would be all lowercased, but... I just liked it this way so that's why I made the first letter uppercase.

This eliminates the need to do extra checking for integers, arrays and objects. E.g., instead of both array and object datatypes returning "object", trueType will return "Array" or "Object";

compareType: function(type1, type2)

This will return a boolean value from the comparison of 2 values.

If type2 (the second argument) is "undefined" it will instead return an object with one property, which is a function. This function is named equalsTypeOf. It accepts one argument, which it assumes is type2. Calling this will compare type1 of the outer function to type2. This is more about semantics here.

typeError: function(wantedType, value)

This is meant more for internal use for the error handling, but if you feel so inclined to use it... it's there! It simply prints a message stating that wantedType (a string) was expected, but instead received value (the actual value, not datatype) of a type.

Object: function(value)

Returns value if it is an object. If it's not an object (as determined by trueType) it will log an error and return an empty object.

Array: function(value)

Returns value if it is an array. If it's not an array (as determined by trueType) it will log an error and return an empty array.

String: function(value)

Returns value if it is a string. If it's not an string (as determined by trueType) it will log an error and return an empty string.

Bool: function(value)

Returns value if it is an boolean. If it's not an boolean (as determined by trueType) it will log an error and return an empty boolean.

Func: function(value)

Returns value if it is a function. If it's not an function (as determined by trueType) it will log an error and return an empty function.

Int: function(value)

Returns value if it is a number. Float values are automatically rounded to the nearest whole number

Float: function(value, fixedValue)

Returns value if it is a number. Although, due to the values you may provide, it may instead turn out to be an integir, the main purpose of Float is to put no limit on the number values that you provide, unlike Int.

fixedValue will return a number value rounded to the n'th place (n, of course, being fixedValue).

Note: Neither Int or Float will throw an error for a number not being an integer of float. This lack of specificity is a limit of the JavaScript language. If you would like to check for these specific differences for numbers you may use the trueType function.

Example usage:

var foo = shType({
  variableName: "foo"
}).String("bar")
console.log(foo); // bar
shType({
  variableName: "foo"
}).trueType(foo); // "String";

var foo = shType({
  variableName: "foo"
}, 0).String(false);// Error!
console.log(foo); // (empty string)
shType({
  variableName: "foo"
}).trueType(foo); "String";