JavaScript (JS)
1. Introduction to JS
var name = "hello";
var age = 19;
var field = "pentrest";
console.log(age);
console.log(name);
console.log(field);
alert(1);
confirm(1);
prompt(1);2. Comments
console.log("Hello from JavaScript"); //in-line comment
/* this is a multi-line comment */3. Data Types and Variables
/* Data Types: undefined, variables, null, bool, string, symbol, number, and object */
var name = "M8SZT8";
name = 8;
let ourname = "group";
const pi = 3.14;4. Storing Variables with the Assignment Operator
var a;
var b = 3;
console.log(a);
a = 7;
b = a;
console.log(a);5. Double Quote
// As in any language
var mystr = "I am a \"double quoted\" string inside \"quoted\"";
var mystr = 'I am a "double quoted" string inside "quoted"';
console.log(mystr);6. Escape Sequences
// Code output: /' single quote/" double quote// backslash/n new line /r carriage return /t tab/b backspace/f form feed7. Bracket Notation
var name = "M8SZT8";
var firstletterofname = "";
firstletterofname = name[0];
console.log(firstletterofname);8. String Immutability
var mystr = "jello world ";
// mystr[0] = "h"; // Error
mystr = "hello world ";
console.log(mystr);9. Find Nth Character
var name = "mszt";
var lastletterofname = name[name.length - 1];
console.log(lastletterofname);
var lastletterofname = name[name.length - 3];
console.log(lastletterofname);10. Word Blanks
function wordBlanks(myNoun, myAdjective, myVerb, myAdverb) {
var result = "";
result += "The " + myAdjective + " " + myNoun + " " + myVerb + " " + "to the store";
return result;
}
console.log(wordBlanks("dog", "big", "ran", "quickly"));11. Arrays
// Example for Arrays
var ourArray = [["the universe", 42], ["everything", 101010]];
var myArray = [["Bulls", 23], ["White Sox", 45]];
// Example for Editing Arrays
var ourArray = [18, 64, 99];
ourArray[1] = 45;
var myArray = [18, 64, 99];
myArray[0] = 45;
console.log(myArray);
// Access Multi-Dimensional Arrays
var myArray = [[1,2,3], [4,5,6], [7,8,9], [[10,11,12], 13, 14]];
var myData = myArray[2][1];
console.log(myData);12. Push()
// Example Push array to other array
var ourArray = ["Stimpson", "J", "cat"];
ourArray.push(["happy", "joy"]);
// Setup
var myArray = [["John", 23], ["cat", 2]];
myArray.push(["dog", 3]);13. Pop()
// Example Remove last element in the array
var ourArray = [1,2,3];
var removedFromOurArray = ourArray.pop();
// Setup
var myArray = [["John", 23], ["cat", 2]];
var removedFromMyArray = myArray.pop();
console.log(myArray);14. Shift() & Unshift()
// Example remove first element from array
var ourArray = ["Stimpson", "J", ["cat"]];
var removedFromOurArray = ourArray.shift();
// Setup
var myArray = [["John", 23], ["dog", 3]];
var removedFromMyArray = myArray.shift();
// unshift add as the first element
removedFromMyArray.unshift("m8szt8");15. Functions
// Example
function ourReusableFunction() {
console.log("Heyya, World");
}
ourReusableFunction();
// Only change code below this line
function reusableFunction() {
console.log("Hi World");
}
reusableFunction();16. Return a Value from a Function
function timesFive(num) {
return num * 5;
}
console.log(timesFive(5));17. If Statements
// Example
function trueOrFalse(wasThatTrue) {
if (wasThatTrue) {
return "Yes, that was true";
}
return "No, that was false";
}
console.log(trueOrFalse(true));18. Comparison with the Equality Operator
function testEqual(val) {
if (val == 12) {
return "Equal";
}
return "Not Equal";
}
console.log(testEqual(10));19. Strict Equality Operator
function testStrict(val) {
if (val === 7) {
return "Equal";
}
return "Not Equal";
}
console.log(testStrict(7));20. Inequality Operator
function testNotEqual(val) {
if (val != 99) {
return "Not Equal";
}
return "Equal";
}
console.log(testNotEqual(10));Certainly! Let's continue with the JavaScript cheat sheet:
21. Strict Inequality Operator
function testStrictNotEqual(val) {
if (val !== "17") {
return "Not Equal";
}
return "Equal";
}
console.log(testStrictNotEqual("17"));22. Greater Than Operator
function testGreaterThan(val) {
if (val > 100) {
return "Over 100";
}
if (val > 10) {
return "Over 10";
}
return "10 or Under";
}
console.log(testGreaterThan(20));23. Greater Than or Equal To Operator
function testGreaterOrEqual(val) {
if (val >= 20) {
return "20 or Over";
}
if (val >= 10) {
return "10 or Over";
}
return "Under 10";
}
console.log(testGreaterOrEqual(15));24. Less Than Operator
function testLessThan(val) {
if (val < 25) {
return "Under 25";
}
if (val < 55) {
return "Under 55";
}
return "55 or Over";
}
console.log(testLessThan(45));25. Less Than or Equal To Operator
function testLessOrEqual(val) {
if (val <= 12) {
return "Smaller Than or Equal to 12";
}
if (val <= 24) {
return "Smaller Than or Equal to 24";
}
return "Greater Than 24";
}
console.log(testLessOrEqual(20));26. Logical And Operator
function testLogicalAnd(val) {
if (val >= 25 && val <= 50) {
return "Yes";
}
return "No";
}
console.log(testLogicalAnd(30));27. Logical Or Operator
function testLogicalOr(val) {
if (val < 10 || val > 20) {
return "Outside";
}
return "Inside";
}
console.log(testLogicalOr(15));28. Else Statements
function testElse(val) {
var result = "";
if (val > 5) {
result = "Bigger than 5";
} else {
result = "5 or Smaller";
}
return result;
}
console.log(testElse(4));29. Else If Statements
function testElseIf(val) {
if (val > 10) {
return "Greater than 10";
} else if (val < 5) {
return "Smaller than 5";
} else {
return "Between 5 and 10";
}
}
console.log(testElseIf(7));30. Switch Statements
function caseInSwitch(val) {
var answer = "";
switch(val) {
case 1:
answer = "alpha";
break;
case 2:
answer = "beta";
break;
case 3:
answer = "gamma";
break;
case 4:
answer = "delta";
break;
}
return answer;
}
console.log(caseInSwitch(2));Certainly! Let's continue with the JavaScript cheat sheet:
31. Default Option in Switch Statements
function switchOfStuff(val) {
var answer = "";
switch(val) {
case "a":
answer = "Apple";
break;
case "b":
answer = "Bird";
break;
case "c":
answer = "Cat";
break;
default:
answer = "Stuff";
break;
}
return answer;
}
console.log(switchOfStuff("b"));32. Multiple Identical Options in Switch Statements
function sequentialSizes(val) {
var answer = "";
switch(val) {
case 1:
case 2:
case 3:
answer = "Low";
break;
case 4:
case 5:
case 6:
answer = "Mid";
break;
case 7:
case 8:
case 9:
answer = "High";
break;
}
return answer;
}
console.log(sequentialSizes(5));33. Returning Boolean Values from Functions
function isLess(a, b) {
return a < b;
}
console.log(isLess(10, 15));34. Return Early Pattern for Functions
function abTest(a, b) {
if (a < 0 || b < 0) {
return undefined;
}
return Math.round(Math.pow(Math.sqrt(a) + Math.sqrt(b), 2));
}
console.log(abTest(2, 2));35. Counting Cards
var count = 0;
function cc(card) {
switch(card) {
case 2:
case 3:
case 4:
case 5:
case 6:
count++;
break;
case 10:
case "J":
case "Q":
case "K":
case "A":
count--;
break;
}
return count > 0 ? count + " Bet" : count + " Hold";
}
console.log(cc(2), cc(3), cc(7), cc('K'), cc('A'));Certainly! Let's continue with the JavaScript cheat sheet:
36. Build JavaScript Objects
var myDog = {
"name": "Spot",
"legs": 4,
"tails": 1,
"friends": ["everything!"]
};37. Accessing Object Properties with Dot Notation
var myObj = {
prop1: "value1",
prop2: "value2"
};
var prop1Value = myObj.prop1; // Accessing property using dot notation38. Accessing Object Properties with Bracket Notation
var myObj = {
"Space Name": "Kirk",
"More Space": "Spock"
};
var propValue = myObj["Space Name"]; // Accessing property with spaces using bracket notation39. Accessing Object Properties with Variables
var myObj = {
prop1: "value1",
prop2: "value2"
};
var prop = "prop1";
var propValue = myObj[prop]; // Accessing property using a variable40. Updating Object Properties
var myObj = {
prop1: "value1",
prop2: "value2"
};
myObj.prop1 = "new value"; // Updating property value41. Add New Properties to a JavaScript Object
var myObj = {
prop1: "value1",
prop2: "value2"
};
myObj.prop3 = "value3"; // Adding a new property42. Delete Properties from a JavaScript Object
var myObj = {
prop1: "value1",
prop2: "value2"
};
delete myObj.prop1; // Deleting a property43. Using Objects for Lookups
function phoneticLookup(val) {
var result = "";
var lookup = {
"alpha": "Adams",
"bravo": "Boston",
"charlie": "Chicago",
"delta": "Denver",
"echo": "Easy",
"foxtrot": "Frank"
};
result = lookup[val];
return result;
}
console.log(phoneticLookup("charlie"));44. Testing Objects for Properties
var myObj = {
prop1: "value1",
prop2: "value2"
};
function checkObj(checkProp) {
return myObj.hasOwnProperty(checkProp) ? myObj[checkProp] : "Not Found";
}
console.log(checkObj("prop1"));45. Manipulating Complex Objects
var myMusic = [
{
"artist": "Billy Joel",
"title": "Piano Man",
"release_year": 1973,
"formats": ["CD", "8T", "LP"],
"gold": true
},
{
"artist": "Michael Jackson",
"title": "Thriller",
"release_year": 1982,
"formats": ["CD", "Cassette", "LP"],
"gold": true
}
];46. Accessing Nested Objects
var myStorage = {
"car": {
"inside": {
"glove box": "maps",
"passenger seat": "crumbs"
},
"outside": {
"trunk": "jack"
}
}
};
var gloveBoxContents = myStorage.car.inside["glove box"];47. Accessing Nested Arrays
var myPlants = [
{
type: "flowers",
list: ["rose", "tulip", "dandelion"]
},
{
type: "trees",
list: ["fir", "pine", "birch"]
}
];
var secondTree = myPlants[1].list[1];48. Record Collection
var recordCollection = {
2548: {
albumTitle: "Slippery When Wet",
artist: "Bon Jovi",
tracks: ["Let It Rock", "You Give Love a Bad Name"]
},
2468: {
albumTitle: "1999",
artist: "Prince",
tracks: ["1999", "Little Red Corvette"]
},
1245: {
artist: "Robert Palmer",
tracks: []
}
};
function updateRecords(records, id, prop, value) {
if (value === "") {
delete records[id][prop];
} else if (prop !== "tracks") {
records[id][prop] = value;
} else {
if (records[id].hasOwnProperty("tracks")) {
records[id].tracks.push(value);
} else {
records[id].tracks = [];
records[id].tracks.push(value);
}
}
return
records;
}49. Iterate with JavaScript While Loops
var myArray = [];
var i = 0;
while (i < 5) {
myArray.push(i);
i++;
}50. Iterate with JavaScript For Loops
var myArray = [];
for (var i = 1; i <= 5; i++) {
myArray.push(i);
}Last updated