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Senior Frontend Interview Questions

Some questions about frontend development that might be in your next job interview. The questions were formulated by @mauvieira, a super senior fullstack developer

General Frontend

• What are the strategies we can use to optimize the performance of web applications?

  • CDNs, GraphQL (maybe) to reduce overfetching, improve backend performance, use SSR and/or SSG, lazy loading for loading assets only when it's needed, minimize and compress HTML, CSS and JS files, and optimize images by compressing and resizing them.

• What are Web Vitals (LCP, FID, CLS)? And how are they applied in the real world?

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import React, { useState, useEffect } from 'react';

function FetchData() {
  const [data, setData] = useState(null);
  const [error, setError] = useState(null);

  useEffect(() => {
    // Create a new AbortController instance
    const abortController = new AbortController();
    const signal = abortController.signal;

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(async () => {
  function sleep(ms) {
    return new Promise((resolve) => setTimeout(resolve, ms));
  }
    
  const acceptButtons = document.querySelectorAll('[aria-label*="Accept"]');
    
  for (const acceptButton of acceptButtons) {
    acceptButton.click()
    await sleep(2000);

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{
  "name": "Arb Whitelist Era",
  "timestamp": "2022-03-01T22:44:18.339Z",
  "version": {
    "major": 4,
    "minor": 2,
    "patch": 0
  },
  "tokens": [
    {

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export const arbitrumTokens =  [
    {
      "logoURI": "https://assets.coingecko.com/coins/images/279/thumb/ethereum.png?1595348880",
      "chainId": 1,
      "name": "Ethereum",
      "address": "0x0000000000000000000000000000000000000000",
      "symbol": "ETH",
      "decimals": 18
    },
    {

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import { gql } from "graphql-request";
// import { returningValues as genericValues } from "./payload";
import { returningValues as genericValues } from "./payload";

export interface IPage {
  /** How many records should be returned on the page */
  limit: number;

  /** Which page should be displayed (starts with 1) */
  page: number;

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Git Submodules basic explanation

Why submodules?

In Git you can add a submodule to a repository. This is basically a repository embedded in your main repository. This can be very useful. A couple of advantages of using submodules:

• You can separate the code into different repositories.

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1 NPM_TOKEN

Add an NPM_TOKEN secret on GitHub. Get your secret key from the NPM dashboard.

2 Add a step to your action

- name: Authenticate with private NPM package
  run: echo "//registry.npmjs.org/:_authToken=${{ secrets.NPM_TOKEN }}" > ~/.npmrc

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const https = require("https");
const fs = require("fs");

const SKIP_PLATFORMS = [
  "tron",
  "sora",
  "factom",
  "elrond",
  "osmosis",
  "cosmos",

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const fs = require("fs");
const axios = require("axios");

const URLS = [
  "https://tokens.uniswap.org",
  "https://extendedtokens.uniswap.org",
  "https://unsupportedtokens.uniswap.org",
  "https://raw.githubusercontent.com/The-Blockchain-Association/sec-notice-list/master/ba-sec-list.json",
  "https://api.coinmarketcap.com/data-api/v3/uniswap/all.json",
  "https://tokens.coingecko.com/uniswap/all.json",