Nov 17

JavaScript — How to create and fill an empty array with a given size?

Solution const arr = Array(5).fill(""); console.log(arr); //prints out ["","","","",""] console.log(arr[0]); //prints out "" 1) To create new array which, you cannot iterate over, you can use array constructor: Array(100) or new…

Java Script

1 min read

Java Script

1 min read

JavaScript — How to create and fill an empty array with a given size?

Solution

const arr = Array(5).fill("");
console.log(arr); //prints out ["","","","",""]
console.log(arr[0]); //prints out ""

1) To create new array which, you cannot iterate over, you can use array constructor:

Array(100) or new…

Nov 10

How to ensure an event listener is only fired once in JavaScript

1. Using the once option We can pass an object as an argument to the addEventListener method and specify that the event is only handled once. This is achieved by passing the property once to the object. If we set once to true, the event will only be fired once. let btn = document.getElementById('btn'); btn.addEventListener("click", function()…

Java Script

1 min read

Java Script

1 min read

Nov 2

JavaScript — How to place a div side by side

Here are 2 ways to place a div side by side. Using CSS float property: <div style="width: 100%; overflow: hidden;"> <div style="width: 600px; float: left;"> Left…

HTML

1 min read

HTML

1 min read

JavaScript — How to place a div side by side

Here are 2 ways to place a div side by side.

Using CSS float property:

<div style="width: 100%; overflow: hidden;">
     <div style="width: 600px; float: left;"> Left…

Nov 1

How to prettify a JSON object on the browser

To prettify a JSON object on the browser, use the <pre> tag. var data = { "data": { "x": "1", "y": "1", "url": "http://url.com" }, "event": "start", "show": 1, "id": 50 } document.getElementById("json").textContent = JSON.stringify(data, undefined, 2); <pre id="json"></pre> pre tells the…

Java Script

1 min read

Java Script

1 min read

How to prettify a JSON object on the browser

To prettify a JSON object on the browser, use the <pre> tag.

var data = {
  "data": {
    "x": "1",
    "y": "1",
    "url": "http://url.com"
  },
  "event": "start",
  "show": 1,
  "id": 50
}


document.getElementById("json").textContent = JSON.stringify(data, undefined, 2);

<pre id="json"></pre>

pre tells the…

Oct 31

Solution to ‘Missing write access to /usr/local/lib/node_modules’ error

What to do when you have this output on the terminal when you try to download a node package with NPM? npm WARN checkPermissions Missing write access to /usr/local/lib/node_modules npm ERR! path /usr/local/lib/node_modules npm ERR! code EACCES npm ERR! errno -13 npm ERR! syscall access npm ERR! Error: EACCES: permission denied, access '/usr/local/lib/node_modules' npm ERR! { [Error: EACCES: permission denied, access '/usr/local/lib/node_modules'] npm ERR! stack: npm ERR! 'Error: EACCES: permission denied, access \'/usr/local/lib/node_modules\'', npm…

Java Script

1 min read

Java Script

1 min read

Oct 28

JavaScript — How to add an eventListener to multiple elements

Method #1: Use a for loop through all input elements let elementsArray = document.querySelectorAll("input"); elementsArray.forEach(function(elem) { elem.addEventListener("input", function() { console.log("CHANGE!"); }); }); Method #2: Listen to the ‘document’ document.addEventListener('click', function(e){ if(e.target.tagName=="BUTTON"){ console.log("CHANGE!"); } }) Explanation: Event Bubbling is the important concept in javascript, so if you can add event on DOM directly, you can save some lines of code, no need for looping.

Java Script

1 min read

Java Script

1 min read

Oct 27

JavaScript — 3 ways to combine an array and remove its duplicates

Method #1: for loop let array1 = ['a','b','c'] let array2 = ['c','c','d','e']; let array3 = []; for(let i=0;i<array1.length;i++){ if(array3.indexOf(array1[i]) == -1) array3.push(array1[i]) } for(let i=0;i<array2.length;i++){ if(array3.indexOf(array2[i]) == -1) array3.push(array2[i]) } return array3; Overall time complexity: Big O(n²) Method #2: using concat and filter (ES5 solution) let array1 = ['a','b','c']

Java Script

1 min read

Java Script

1 min read

Oct 26

JavaScript — Comparison between ‘for loop’ vs. ‘forEach’

for loop for loops are much more efficient. It is a looping construct specifically designed to iterate while a condition is true, at the same time offering a stepping mechanism (generally to increase the iterator). Example: for (var i=0, n=arr.length; i < n; ++i ) { ... } This isn’t to suggest…

Java Script

3 min read

Java Script

3 min read

Oct 24

React.js — Create a table with expand functionality using react-table

Here is the code on how to click a a row to expand using react-table. index.js import React from "react"; import { render } from "react-dom"; import { makeData, Logo, Tips } from "./Utils"; // Import React Table import ReactTable from "react-table"; import "react-table/react-table.css"; const columns = [ { Header…

React

2 min read

React

2 min read

Oct 17

How to check if an object is a JSON object in Javascript

Answer Use the constructor attribute to check if an object is a JSON object in Javascript. Code var testingObject = {}; if (testingObject && testingObject.constructor === ({}).constructor) { console.log("It's a JSON object!"); } else { console.log("It's NOT a JSON object!"); } Explanation First make sure that that the object is not null. Then…

Java Script

1 min read

Java Script

1 min read