Sam's Typescript utilities

Just a heap of helper functions. That are useful for most of my projects.

Array

• chunkArray - Splits an array into chunks of a set size (very useful for AWS SSM given the 10 item limit)
• groupBy - Pass a function to group items in an array, function should return the group field

Functions

• isFalsy - simple wrapper for a falsy check to make code more readable
• isNullish - simple wrapper to test if something is NULL or UNDEFINED
• sleep - Promise for a sleep timer

Object

• mapObject - Map command to run on an object rather than array
• filterObject - Filter command to run on an object rather than array

Strings

• pascalCase - Converts a string to pascal case -> PascalCase
• camelCase - Converts a string to camel case -> camelCase
• capitalise - Capitalises a word
• capitaliseAllWords - Capitalises all words
• pluralise - Adds s when relevant to words (ie. 1 of something no s, 2 adds s)

TryCatch

• tryCatch - Theo's tryCatch function to convert a try/catch block into something similar to Go error handling

Types

• Nullish - null or undefined
• Nullable - a type that can be the type or Nullish
• ValueOf - a union of all possible values in an object
• Falsy - any false type
• UnionResolver - Converts a basic union into a structured object - usage example below
• OmitMethods - Object without methods, only fields
• Branded - Forces a type to be a certain subset - eg. you have a hash function that returns a string, but you only want another method to accept a string that has gone through that hash - so this "brands" it with a mark.

Union Resolver Example

type ActionType = 'ADD_TODO' | 'REMOVE_TODO' | 'UPDATE_TODO';

type ResolvedActions = UnionResolver<ActionType>;

// The resulting type will be:
// {
//   type: "ADD_TODO";
// }[] | {
//   type: "REMOVE_TODO";
// }[] | {
//   type: "UPDATE_TODO";
// }[]

const actions: ResolvedActions = [
  { type: 'ADD_TODO' },
  { type: 'REMOVE_TODO' },
  { type: 'UPDATE_TODO' },
];

// Now you can handle each action type distinctly
actions.forEach((action) => {
  switch (action.type) {
    case 'ADD_TODO':
      console.log('Adding a todo');
      break;
    case 'REMOVE_TODO':
      console.log('Removing a todo');
      break;
    case 'UPDATE_TODO':
      console.log('Updating a todo');
      break;
  }
});

Branded Example

const HashedStr = Branded<string, 'Hash'>;
const hashFn = (str: string): HashedStr => {
  return (str + 'ThisShouldBeHashed') as HashedStr;
};
const functionStringShouldBeHashed = (hash: HashedStr) => {
  // Do Someething with hash value
};
const str = 'ABC';
functionStringShouldBeHashed(str); // Error
functionStringShouldBeHashed(hashFn(str)); // No error now because of the brand