Use the NestJS Interceptor

The @odata-filter/nestjs interceptor automatically parses the filter query-string parameter on every incoming request and attaches the parsed result to request.query.filterParsed.

npm i @odata-filter/core @odata-filter/validation @odata-filter/nestjs --save

Basic Setup

import { Controller, Get, Query, UseInterceptors } from '@nestjs/common';
import { ODataFilterInterceptor } from '@odata-filter/nestjs';

const schema = {
  country: { type: 'string' },
  age: { type: 'number' },
};

@Controller()
export class AppController {
  @Get('/')
  @UseInterceptors(new ODataFilterInterceptor({ schema }))
  getRoot(@Query() query) {
    const { filter, filterParsed } = query;
    console.log('Raw:', filter);       // "country eq 'US'"
    console.log('Parsed:', filterParsed);
    /*
    {
      type: 'comparison_operator',
      value: 'eq',
      left: { type: 'field', value: 'country' },
      right: { type: 'string_value', value: 'US' }
    }
    */
    return filterParsed;
  }
}

With MongoDB Marshaling

Pass format: 'mongo-json' to receive a MongoDB query object instead of the raw AST.

@Get('/')
@UseInterceptors(new ODataFilterInterceptor({ schema, format: 'mongo-json' }))
getRoot(@Query() query) {
  const { filter, filterParsed } = query;
  console.log('Raw:', filter);       // "country eq 'US'"
  console.log('Parsed:', filterParsed); // { country: 'US' }
  return filterParsed;
}

With SQL Marshaling

Pass format: 'sql' to receive a SQL WHERE clause string instead of the raw AST.

@Get('/')
@UseInterceptors(new ODataFilterInterceptor({ schema, format: 'sql' }))
getRoot(@Query() query) {
  const { filter, filterParsed } = query;
  console.log('Raw:', filter);       // "country eq 'US'"
  console.log('Parsed:', filterParsed); // "country = 'US'"
  return filterParsed;
}