.push is not a function in web crawler - node.js

Question

I am writing a node JS web crawler class, and I have encountered the following error, this.textInvertedIndex[word].push is not a function. Upon further inspection I realised that for some reason this.textInvertedIndex[word] was written as a native object, function Object({ [native code] }). For the first few iterations, by console logging this.textInvertedIndex everything seemed fine as it was an object of arrays. But then suddenly this error occurred. Is there any part of the code where I am implicitly rewriting textInvertedIndex?
Here is the relevant class:
function Crawler(queue, maxIndexSize) {
this.queue = queue;
this.maxIndexSize = maxIndexSize;
this.findChunks = () => {
let currentChunk;
let minimumDistance = Infinity;
for (i = 1; i <= this.maxIndexSize; i++) {
if (this.maxIndexSize % i === 0) {
const newDistance = Math.abs(i - 30);
if (newDistance < minimumDistance) {
minimumDistance = newDistance;
currentChunk = i;
} else {
return currentChunk
};
};
};
};
this.chunks = this.findChunks();
this.chunkSize = this.maxIndexSize / this.chunks;
this.totalWordOccurances = {};
this.imageInvertedIndex = {};
this.textInvertedIndex = {};
this.images = [];
this.sites = [];
this.seen = {};
this.write = (url, html) => {
const documentId = this.sites.length;
const website = new Website(url, html);
const title = website.title();
const content = website.content(title);
const words = content.filter(item => typeof item !== "object");
const wordsLength = words.length;
const query = new Query(words);
const individualWords = query.individualize(words);
this.seen[url] = true;
this.sites.push({
url,
title,
description: website.description()
});
for (word of individualWords) {
const normalizedTf = query.count(word) / wordsLength;
const textInvertedIndexEntry = {
documentId,
normalizedTf
};
if (this.textInvertedIndex[word]) {
this.textInvertedIndex[word].push(textInvertedIndexEntry);
} else {
this.textInvertedIndex[word] = [textInvertedIndexEntry];
};
if (this.totalWordOccurances[word]) {
this.totalWordOccurances[word] += 1;
} else {
this.totalWordOccurances[word] = 1;
};
};
for (i = 0; i < content.length; i++) {
const item = content[i];
if (typeof item === "object") {
const imageId = this.images.length;
this.images.push(item);
for (word of individualWords) {
const imageScore = getImageScore(i, word, content);
const imageInvertedIndexEntry = {
imageId,
imageScore
};
if (this.imageInvertedIndex[word]) {
this.imageInvertedIndex[word].push(imageInvertedIndexEntry);
} else {
this.imageInvertedIndex[word] = [imageInvertedIndexEntry];
};
};
};
};
};
this.crawl = async () => {
while (this.sites.length !== this.maxIndexSize) {
let nextQueue = [];
const websitesUnfiltered = await Promise.all(this.queue.map((url) => {
const website = new Website(url);
return website.request();
}));
const websitesToAdd = this.maxIndexSize - this.sites.length;
let websites = websitesUnfiltered.filter(message => message !== "Failure")
.slice(0, websitesToAdd);
for (site of websites) {
const url = site.url;
const htmlCode = site.htmlCode;
const website = new Website(url, htmlCode);
this.write(url, htmlCode);
nextQueue = nextQueue.concat(website.urls());
};
nextQueue = new Query(nextQueue.filter(url => !this.seen[url]))
.individualize();
this.queue = nextQueue;
};
};
};
Called like this
const crawler = new Crawler(["https://stanford.edu/"], 25000000);
crawler.crawl();

Answer 1

this.textInvertedIndex = {}; is defining an Object of which push is not a valid function. you can change it to an array by defining it as this.textInvertedIndex = []; otherwise you can add key/value entries to the object as it is defined like this: this.textInvertedIndex[key] = value;

Answer 2

Turns out, my key was accessing this.textInvertedIndex[word]. And word was constructor. constructor is already a built in object property so it can never be rewritten as an array with .push defined. To solve this problem, make all object keys capital, so constructor will become CONSTRUCTOR, thus making sure that already existing object properties are never called.