ad-hoc-json-filter

Filtering JSON data with variable filter conditions at runtime.

$ npm install ad-hoc-json-filter

Why?

Filtering JSON in JS is simple. At least when you know the filter conditions at dev time.

But when it comes to runtime (for example if you offered variable filter inputs to your users), the filter conditions (except the values itself) can't be changed as the code can't change at runtime.

That's the point this library is intended for.

How?

Build an array like this:

[
  { key: 'details.age', op: '>=', value: 18 }, 
  { key: 'isActive', op: '=', value: true },
  { key: 'registration', op: '<=', value: '2020-01-01' },
  { grp: '(' }
    { key: 'details.address.state', op: '=', value: 'Colorado' }, 
    { con: '||' }, 
    { key: 'details.address.state', op: '=', value: 'California' }, 
  { grp: ')' }
]

That's it. Just put your JSON array and the filter array into the filter function and be happy.

The details!

The filter() function takes a JSON array and a filter array and will return the filtered result as new array:

function filter(json: Array<unknown>, filterExpressions: Array<expressionFilter | expressionConnector | expressionGroup>);

The json parameter must be an array with JSON objects (not stringified JSON!).

The filterExpressions parameter can contain three different types of filter expressions:

type expressionFilter = {
    key: string; // The property/sub-property name to filter
    op: '=' | '!=' | '<' | '<=' | '>' | '>=' | 'cont' | 'sw' | 'ew'; // The comarison operation to perform
    val: string | number | boolean | null; // The value to compare with
};
type expressionConnector = {
    con: '&&' | '||'; // AND / OR connection
};
type expressionGroup = {
    grp: '(' | ')'; // Opening or closing a group
};

If you don't pass a 'expressionConnector' between each 'expressionFilter', they will automatically be connect with AND logic.

If you pass a string as filter value, but the data value isn't a string, the lib will perform a .toString() on number | bigint | boolean and a .toISOString() on Date. A null value in the data will be compared as 'null'.

And always remember: shit in, shit out :)