JavaScript tips

Declare JS variables

• var one = 1; (function scoped, available before declaration) (no need to var anymore)
• let two = 2; (block scoped, only available after declaration) (use in loops)
• const three = 3; (block scoped, cannot be changed) (use by default)

Converting between numbers and strings

• parseInt() / parseFloat()
• toString()

Manipulating Arrays

• push and pop - affects end of array eg:
  • array.push(values)
  • array.pop()
• shift and unshift - affects front of array eg:
  • array.shift()
  • array.unshift(values)
• concat - joins two arrays to make a new array

Loops in JavaScript

• while

const names = ['Justin','Sarah','Christopher'];
let index = 0;
while (index < names.length) {
	const name = names[index];
	console.log(name);
	index++;
}

• for

const names = ['Justin','Sarah','Christopher'];
for (let index = 0; index < names.length; index++) {
	const name = names[index];
	console.log(name);
}

• for … of

const names = ['Justin','Sarah','Christopher'];
for (const name of names) {
	console.log(name);
}

Function Syntax

function computePrice(cost, discount){
	let reduction = cost*discount;
	console.log("You saved $"+reduction);
	return cost-reduction;
}

JSON Things to know

• Stringify: Serialize Object to JSON
  • eg: let bookJSON = JSON.stringify(book); // stringify - object input
  • eg: let myBooksJSON = JSON.stringify(myBooks); // stringify - collection inupt
• Parse: Deserialize JSON to Object
  • examaple:

	data = bookJSON;
	let parsed = JSON.parse(data);
	console.log(parsed);

	data = myBooksJSON;
	parsed = JSON.parse(data);
	console.log(parsed);
	console.log("Author of 2nd book: "+parsed[1].author);