Ignore is a token item filter based on Replace, which is used to remove values completely.

Introduction

const {ignore} = require('stream-json/filters/Ignore');
const {parser} = require('stream-json/Parser');
const {streamArray} = require('stream-json/streamers/StreamArray');

const pipeline = chain([
  fs.createReadStream('sample.json'),
  parser(), // packs keys by default, otherwise {packKeys: true}
  ignore({filter: /\bmeta\b/i}),
  streamArray()
]);

pipeline.on('data', data => console.log(data));

In order to use this filter make sure that a filter gets packed keys.

API

This is a helper class based on Replace. See Replace for more details.

The whole implementation is very simple:

class Ignore extends Replace {
  constructor(options) {
    super(options);
    this._replacement = Replace.arrayReplacement([]);
    this._allowEmptyReplacement = true;
  }
}

Effectively it is Replace with a replacement set to [], and allowEmptyReplacement is set to true.

The following options are used:

• filter
  • If it returns a truthy value, the current object is removed completely with all its possible subobjects.
  • It is called only for the following tokens: startObject, startArray, startString, startNumber, stringValue, numberValue, nullValue, trueValue, falseValue.
• pathSeparator
• once

Static methods and properties

It uses the same set of static methods and properties as Replace. The differences:

• It uses Ignore as a class for all instances.
• Its factory function is called ignore() instead of replace().