@loaders.gl/json/dist/lib/json-parser/streaming-json-parser.js

Framework-independent loader for JSON and streaming JSON formats

// loaders.gl
// SPDX-License-Identifier: MIT
// Copyright (c) vis.gl contributors
import { default as JSONParser } from "./json-parser.js";
import JSONPath from "../jsonpath/jsonpath.js";
/**
 * The `StreamingJSONParser` looks for the first array in the JSON structure.
 * and emits an array of chunks
 */
export default class StreamingJSONParser extends JSONParser {
    jsonPaths;
    streamingJsonPath = null;
    streamingArray = null;
    topLevelObject = null;
    constructor(options = {}) {
        super({
            onopenarray: () => {
                if (!this.streamingArray) {
                    if (this._matchJSONPath()) {
                        // @ts-ignore
                        this.streamingJsonPath = this.getJsonPath().clone();
                        this.streamingArray = [];
                        this._openArray(this.streamingArray);
                        return;
                    }
                }
                this._openArray();
            },
            // Redefine onopenarray to inject value for top-level object
            onopenobject: (name) => {
                if (!this.topLevelObject) {
                    this.topLevelObject = {};
                    this._openObject(this.topLevelObject);
                }
                else {
                    this._openObject({});
                }
                if (typeof name !== 'undefined') {
                    this.parser.emit('onkey', name);
                }
            }
        });
        const jsonpaths = options.jsonpaths || [];
        this.jsonPaths = jsonpaths.map((jsonpath) => new JSONPath(jsonpath));
    }
    /**
     * write REDEFINITION
     * - super.write() chunk to parser
     * - get the contents (so far) of "topmost-level" array as batch of rows
     * - clear top-level array
     * - return the batch of rows\
     */
    write(chunk) {
        super.write(chunk);
        let array = [];
        if (this.streamingArray) {
            array = [...this.streamingArray];
            this.streamingArray.length = 0;
        }
        return array;
    }
    /**
     * Returns a partially formed result object
     * Useful for returning the "wrapper" object when array is not top level
     * e.g. GeoJSON
     */
    getPartialResult() {
        return this.topLevelObject;
    }
    getStreamingJsonPath() {
        return this.streamingJsonPath;
    }
    getStreamingJsonPathAsString() {
        return this.streamingJsonPath && this.streamingJsonPath.toString();
    }
    getJsonPath() {
        return this.jsonpath;
    }
    // PRIVATE METHODS
    /**
     * Checks is this.getJsonPath matches the jsonpaths provided in options
     */
    _matchJSONPath() {
        const currentPath = this.getJsonPath();
        // console.debug(`Testing JSONPath`, currentPath);
        // Backwards compatibility, match any array
        // TODO implement using wildcard once that is supported
        if (this.jsonPaths.length === 0) {
            return true;
        }
        for (const jsonPath of this.jsonPaths) {
            if (jsonPath.equals(currentPath)) {
                return true;
            }
        }
        return false;
    }
}