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Learning Your Second Language

What you will learn

  • Creating Variables in a New Language
  • Conditionals in a New Language
  • Looping in a New Language
  • Collections in a New Language
  • Writing Functions in a New Language

Getting Started

Head over to Repl.it and create a new REPL to practice today's New Language!

Creating Variables

How we did it in Javascript

// We create constant variables with the const keyword
const myConstant = 5;
// We create re-assignable variables with the let keyword
let myVariable = "Hello World";

// We Printed Variables to the console using console.log
console.log(myConstant);
console.log(myVariable);

How we do this in Golang

package main

//import fmt library for fmt.Println for printing to console
import "fmt"

// Create constant variables with const keyword
const MY_CONST = 5
// variables declared with var keyword, require type declarations
var my_variable string = "Hello World"

func main(){
    fmt.Println(MY_CONST)
    fmt.Println(my_variable)
}

Receiving Input

In Javascript we could either use forms, prompt to receive input from the user on the frontend. In node, getting input from the console is a bit more complicated, let's see how we would do that in nodeJS.

// Import Readline Node Library and Create Interface to Read Input
const readline = require("readline").createInterface({
  input: process.stdin,
  output: process.stdout,
});

// Ask questions, receive input, run callback in response
readline.question("Who are you?", (name) => {
  console.log(`Hey there ${name}!`);
  readline.close();
});

How would we do that in Golang?

// Golang program to show how
// to take input from the user
package main

import "fmt"

// main function
func main() {

    // Println function is used to
    // display output in the next line
    fmt.Println("Who are you: ")

    // var then variable name then variable type
    var name string

    // Taking input from user
    fmt.Scanln(&name)

    // Use Results
    fmt.Print("Hey there... " + name)
}

Conditionals

If statements in Javascript

const num = 5;

if (num > 3) {
  console.log("num is greater than 3");
} else if (num > 1) {
  console.log("num is greater than 1");
} else {
  console.log("num is 1 or less");
}

If statements in Golang

// Golang program to show how
// to take input from the user
package main

import "fmt"

// main function
func main() {
num := 5 // Type is implied when using := operator to create variables

if num > 3 {
  fmt.Println("num is greater than 3")
} else if num > 1 {
  fmt.Println("num is greater than 1")
} else {
  fmt.Println("num is 1 or less")
}
}

While Loops

In Javascript

let counter = 0;

//This will loop 10 times
while (counter < 10) {
  console.log(counter);
  counter += 1;
}

In Golang

package main

import "fmt"

// main function
func main() {
counter := 0

//This will loop 10 times
// No While loops in go, but can get same effect by not including the first and third part of the for
for ;counter < 10; {
  fmt.Println(counter);
  counter += 1;
}
}

10 Minute Exercise

Write the code to do the following:

  • Loop 10 times starting the counter at 0
  • On each loop if the counter is even print "it's even"
  • If odd, print "meow" if the number is divisble by 3
  • Otherwise print nothing

Collections

In Javascript we have arrays and objects

const myArray = [1, 2, 3];

console.log(myArray); //logging the entire array
console.log(myArray[0]); // logging an individual item

const myObject = {
  cheese: "gouda",
  bread: "rye",
};

console.log(myObject); //logging the entire object
console.log(myObject.cheese); // logging a property using dot notation
console.log(myObject["bread"]); // logging a property using square bracket notation

In Golang we will use slices and maps

package main

import "fmt"

// main function
func main() {
mySlice := []int{1,2,3}; // This dynamic array like structure is called a slice

fmt.Println(mySlice); //logging the entire slice
fmt.Println(mySlice[0]); // logging an individual item

myMap := map[string]string{
  "cheese": "gouda",
  "bread": "rye",
} // Creating a map, the key and values must be typed

fmt.Println(myMap); //logging the entire object
fmt.Println(myMap["cheese"]); //accessing map properties
fmt.Println(myMap["bread"]);
}

10 Minute Exercise

Google Golang Slice Methods/Functions and discover the following and apply them to the following list.

[1,2,3,4,5,6,7,8,9,10]
  • How to find a lists length
  • How to loop over a list
  • How to add and remove items from a list

Functions

in Javascript

const addNums = (x, y) => {
  return x + y;
};

console.log(addNums(5, 5));

In Golang

package main

import "fmt"

// Define function, parameters and return values must be typed
func addNums (x int,y int) int {
  return x + y
}

// main function
func main() {

// Print return value of function
fmt.Println(addNums(5,5))

}

10 minute exercise

Write the following functions

  • sub_nums that takes two arguments and returns their difference
  • say_hello that takes a name as an arguments and says hello to that name
  • sayhelloadv that takes a dictionary with a name and age property and prints "hello {name}, how does it feel to be {age} years old"
  • looper takes one array as an argument, it loops over the array and prints each item individually

Resources to Learn More