Category: JavaScript

JavaScript For Of

The For Of Loop

The JavaScript for of statement loops through the values of an iterable object.

It lets you loop over iterable data structures such as Arrays, Strings, Maps, NodeLists, and more:

Syntax

for (variable of iterable) {
  // code block to be executed
}

variable – For every iteration the value of the next property is assigned to the variable. Variable can be declared with const, let, or var.

iterable – An object that has iterable properties. Continue reading JavaScript For Of

JavaScript For In

The For In Loop

The JavaScript for in statement loops through the properties of an Object:

Syntax

for (key in object) {
  // code block to be executed
}

Example

const person = {fname:"John", lname:"Doe", age:25};

let text = "";
for (let x in person) {
  text += person[x];
}

Example Explained

  • The for in loop iterates over a person object
  • Each iteration returns a key (x)
  • The key is used to access the value of the key
  • The value of the key is person[x]

Continue reading JavaScript For In

JavaScript For Loop

Loops can execute a block of code a number of times.

JavaScript Loops

Loops are handy, if you want to run the same code over and over again, each time with a different value. Continue reading JavaScript For Loop

JavaScript Switch Statement

The switch statement is used to perform different actions based on different conditions.

The JavaScript Switch Statement

Use the switch statement to select one of many code blocks to be executed.

Syntax

switch(expression) {
  case x:
    // code block
    break;
  case y:
    // code block
    break;
  default:
    // code block
}

This is how it works:

  • The switch expression is evaluated once.
  • The value of the expression is compared with the values of each case.
  • If there is a match, the associated block of code is executed.
  • If there is no match, the default code block is executed.

Continue reading JavaScript Switch Statement

JavaScript if, else, and else if

Conditional statements are used to perform different actions based on different conditions.

Conditional Statements

Very often when you write code, you want to perform different actions for different decisions.

You can use conditional statements in your code to do this.

In JavaScript we have the following conditional statements :

  • Use if to specify a block of code to be executed, if a specified condition is true
  • Use else to specify a block of code to be executed, if the same condition is false
  • Use else if to specify a new condition to test, if the first condition is false
  • Use switch to specify many alternative blocks of code to be executed

The switch statement is described in the next chapter.

Continue reading JavaScript if, else, and else if

JavaScript Booleans

A JavaScript Boolean represents one of two values: true or false.

Boolean Values

Very often, in programming, you will need a data type that can only have one of two values, like

  • YES / NO
  • ON / OFF
  • TRUE / FALSE

For this, JavaScript has a Boolean data type. It can only take the values true or false. Continue reading JavaScript Booleans

JavaScript Random

Math.random()

Math.random() returns a random number between 0 (inclusive),  and 1 (exclusive):

Example

// Returns a random number:
Math.random();

Math.random() always returns a number lower than 1.

JavaScript Random Integers

Math.random() used with Math.floor() can be used to return random integers.

There is no such thing as JavaScript integers.

We are talking about numbers with no decimals here.

Continue reading JavaScript Random

JavaScript Math Object

The JavaScript Math object allows you to perform mathematical tasks on numbers.

Example

Math.PI;

The Math Object

Unlike other objects, the Math object has no constructor.

The Math object is static.

All methods and properties can be used without creating a Math object first. Continue reading JavaScript Math Object

JavaScript Set Date Methods

Set Date methods let you set date values (years, months, days, hours, minutes, seconds, milliseconds) for a Date Object.

Set Date Methods

Set Date methods are used for setting a part of a date:

Method Description
setDate() Set the day as a number (1-31)
setFullYear() Set the year (yyyy)
setHours() Set the hour (0-23)
setMilliseconds() Set the milliseconds (0-999)
setMinutes() Set the minutes (0-59)
setMonth() Set the month (0-11)
setSeconds() Set the seconds (0-59)
setTime() Set the time (milliseconds since January 1, 1970)

The setFullYear() Method

The setFullYear() method sets the year of a date object. In this example to 2020 : Continue reading JavaScript Set Date Methods

JavaScript Get Date Methods

The new Date() Constructor

In JavaScript, date objects are created with new Date().

new Date() returns a date object with the current date and time.

Get the Current Time

const date = new Date();

Date Get Methods

Method Description
getFullYear() Get year as a four digit number (yyyy)
getMonth() Get month as a number (0-11)
getDate() Get day as a number (1-31)
getDay() Get weekday as a number (0-6)
getHours() Get hour (0-23)
getMinutes() Get minute (0-59)
getSeconds() Get second (0-59)
getMilliseconds() Get millisecond (0-999)
getTime() Get time (milliseconds since January 1, 1970)

Note 1

The get methods above return Local time.

Universal time (UTC) is documented at the bottom of this page.

Continue reading JavaScript Get Date Methods