Basic JavaScript Knowledge
var x = 5;
var y = 6;
var z = x + y;
z
let text = "Mort";
text
let text2 = 'Yeung';
text2
let number = 1234567890123456789012345n;
let Largenum = BigInt(1234567890123456789012345)
let typeLargenum = typeof Largenum;
typeLargenum
Largenum
Boolean(10 > 9)
Write a boolean statement that outputs true
Boolean(9 > 1)
let name;
name
grade = undefined;
let result;
result = Boolean(undefined);
console.log(result); // false
result = Boolean(null);
console.log(result); // false
7. Symbol: used to represent unique values that can be used as identifiers/keys in objects.
- They are also used to create private properties and methods in classes.
- unique and immutable, so they can be used as unique identifiers in objects and classes.
- useful for creating constants that can be shared across different parts of your code.
// Create a Symbol
const mySymbol = Symbol();
console.log(mySymbol);
// expected output: Symbol()
const myObject = {
[mySymbol]: 'Hello World'
};
console.log(myObject);
Edit/add to the code above so that it outputs "Hello World"
const myObject = {
'Hello World'
};
console.log(myObject);
Object
- Identify the name/keys in the object below: Elly, Rottweiler, 4
- Identify the values in the object below: name, breed, age
const dogs = {name: "Elly", breed:"Rottweiler", age:4, color:"black"}
dogs
Array
const songs = ["Love Story", "Blank Space", "I Knew You Were Trouble"];
songs
const cost1 = 2;
const cost2 = 11;
let totalCost = cost1 + cost2;
totalCost
Conditionals: control behavior, decides whether or not pieces of code can run.
- If: if a condition is true it is used to specify execution for a block of code.
- Else: if the same condition is false it specifies the execution for a block of code.
- Else If: new test if the first condition is false.
if (10 > 5) {
var outcome = "True";
}
outcome;
if ("red" === "blue") {
var outcome = "if block";
} else {
var outcome = "else block";
}
outcome;
let temperature = 54
if (temperature < 70) {
cast = "Chilly";
} else if (temperature < 60) {
cast = "Cold";
} else {
cast = "Warm";
}
cast
Create a conditional statement about how you would greet someone based on the time of day.
let greeting = 54
if (present = true) {
cast = "Hello";
}
else {
cast = "Bye";
}
cast
Iteration:
- for loop: repeats until a specified condition evaluates to false
- do...while: repeats until a specified condition evaluates to false
- while statement: executes its statements as long as a specified condition evaluates to true
- label: provides a statement with an identifier that lets you refer to it later in the code. ex. you can use a label to identify a loop, and then use the break or continue statements to indicate whether a program should interrupt the loop or continue its execution
- break: used to terminate a loop, switch, or in conjunction with a labeled statement
- continue: can be used to restart a while, do-while, for, or label statement
- for...in: iterates a specified variable over all the enumerable properties of an object
- for...of statement creates a loop Iterating over iterable objects, invoking a custom iteration hook with statements to be executed for the value of each distinct property
JavaScript in HTML- Questions
Where do you store the JavaScript Code? You can store it in a js file and the name of the file mustt end in js. (ex. example.js)
How do you import a JS file into HTML? Either you import it from an external js file or you just imbed it into the html file using script tags.
What is onClick? It is the push of a button. When you use onclick, the whenever you push a button that uses this there is supposed to be some output that comes out after pressing the button, which is a result of the onclick function.
What tag do you use to write JavaScript code? You use script tags