quangnd

Exercise 1 - Leap year

You are given a year, determine if it’s a leap year. A leap year is a year containing an extra day. It has 366 daysinstead of the normal 365 days. The extra day is added in February, which has 29 days instead of the normal 28 days. Leap years occur every 4 years. 2012 was a leap year and 2016 will also be a leap year.

The above rule is valid except that every 100 years special rules apply. Years that are divisible by 100 are not leap years if they are not also divisible by 400. For example 1900 was not a leap year, but 2000 was. Print Leap year! or Not a leap year! depending on the case.

Hint: Use the remainder (%) operator to check for divisibility by 4. Don’t forget to check the special case when year is divisible by 100.

let year = 2014

quangnd

VS Code Shell Shortcut for Git Bash

Put this file code in C:\Users\<username>\AppData\Local\Code\bin aside code.cmd.

Assuming this path is already in your %PATH% you can now run the command to open a file

code file.txt

quangnd

{
    "AL": "Alabama",
    "AK": "Alaska",
    "AS": "American Samoa",
    "AZ": "Arizona",
    "AR": "Arkansas",
    "CA": "California",
    "CO": "Colorado",
    "CT": "Connecticut",
    "DE": "Delaware",

quangnd

Error: /usr/local must be writable! on MacOS Sierra

Solution

sudo chgrp -R admin /usr/local
sudo chmod -R g+w /usr/local

---

quangnd

// Flat 2D array to 1D arry

var arr=[[1,2],[3,4],[5,6]];
var result=[].concat(...arr);
console.log(result);    //output: [ 1, 2, 3, 4, 5, 6 ]
// ------------------------

// Produce a specified number of repeating characters:
function repeat(s,n){
  return [...Array(n+1)].join(s);

quangnd

//Example 1 - Calculate average value of an array (transform array into a single number)
  var scores = [89, 76, 47, 95]
  var initialValue = 0
  var reducer = function (accumulator, item) {
    return accumulator + item
  }
  var total = scores.reduce(reducer, initialValue)
  var average = total / scores.length
/*Explain about function

quangnd

import React from "react";
import { render } from "react-dom";

const ParentComponent = React.createClass({
  getDefaultProps: function() {
    console.log("ParentComponent - getDefaultProps");
  },
  getInitialState: function() {
    console.log("ParentComponent - getInitialState");
    return { text: "" };

quangnd

//Original link: http://jaketrent.com/post/send-props-to-children-react/

function RadioOption(props) {
  return (
    <label>
      <input type="radio" value={props.value} name={props.name} />
      {props.label}
    </label>
  )
}

quangnd

/*
Coding in function infiniteLoop. function accept 3 parameters. The 1st parameter is arr, it's a 2D array, it contains three 1D array. The 2nd parameter is d ，it's a string. The 3rd parameter is n, it's a number.

You can think of arr as a moat, the elements of arr like water constantly flow in. The direction of flow is controlled by the parameter d. The value of d can be "left" or "right". "left" means the "river" moves to the left. All elements in the 1D array are to the left moving n position, if beyond the bounds of the array and the element is moved to the tail on the left side of the array; if it exceeds the left boundary element would be moved to the tail of 3rd array(like a circle). Right is also similar to the operation, but it is moving to the right.

Finally, return arr.

Example:
  infiniteLoop( [[1,2,3],[4,5,6],[7,8,9]],"left",1) 
  should return [[2,3,4],[5,6,7],[8,9,1]]

quangnd

// Approach 1: Use React.createClass
var HelloWorld = React.createClass({
  getInitialState() {
    return { message: 'Hi' };
  },

  logMessage() {
    // this magically works because React.createClass autobinds.
    console.log(this.state.message);
  },