Quickstart — Node.js Runtime

Get up and running with @odata-filter/core in a Node.js project in under five minutes.

1. Install

npm i @odata-filter/core --save

2. Tokenize a Filter Expression

import { tokenize } from '@odata-filter/core';

const tokens = tokenize("country/name eq 'US' and age gte 21");
console.log(tokens);

tokenize returns a flat array of typed Token objects representing each element of the filter string.

3. Parse into an AST

import { tokenize, parse } from '@odata-filter/core';

const tokens = tokenize("country/name eq 'US' and age gte 21");
const ast = parse(tokens);

console.log(JSON.stringify(ast, null, 2));
/*
{
  "type": "logical_operator",
  "value": "and",
  "left": {
    "type": "comparison_operator",
    "value": "eq",
    "left": { "type": "field", "value": "country/name" },
    "right": { "type": "string_value", "value": "US" }
  },
  "right": {
    "type": "comparison_operator",
    "value": "gte",
    "left": { "type": "field", "value": "age" },
    "right": { "type": "number_value", "value": 21 }
  }
}
*/

parse returns a tree of Node objects. Each node has a type, a value, and optional left and right children for binary operators.

4. Traverse the AST

Use iterate to perform a depth-first walk over the tree and receive every node in order.

import { tokenize, parse, iterate } from '@odata-filter/core';

const tokens = tokenize("country eq 'US' and age gte 21");
const ast = parse(tokens);
const nodes = iterate(ast);

nodes.forEach(node => console.log(node.type, node.value));

5. Validate Against a JSON Schema

import { tokenize, parse } from '@odata-filter/core';
import { validate } from '@odata-filter/validation';

const ast = parse(tokenize("age gte 21"));

validate(ast, {
  age: { type: 'number' },
});
// No error thrown — the field type matches the operator.

6. Convert to a MongoDB Query

import { tokenize, parse } from '@odata-filter/core';
import { toMongoJson } from '@odata-filter/marshalers';

const ast = parse(tokenize("country eq 'US' and age gte 21"));

console.log(toMongoJson(ast));
/*
{
  "$and": [
    { "country": { "$eq": "US" } },
    { "age": { "$gte": 21 } }
  ]
}
*/