Javascript for range in numbers

JavaScript For Loop

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

Often this is the case when working with arrays:

Instead of writing:

text += cars[0] + «
«;
text += cars[1] + «
«;
text += cars[2] + «
«;
text += cars[3] + «
«;
text += cars[4] + «
«;
text += cars[5] + «
«;

You can write:

Different Kinds of Loops

JavaScript supports different kinds of loops:

• for — loops through a block of code a number of times
• for/in — loops through the properties of an object
• for/of — loops through the values of an iterable object
• while — loops through a block of code while a specified condition is true
• do/while — also loops through a block of code while a specified condition is true

The For Loop

The for statement creates a loop with 3 optional expressions:

Expression 1 is executed (one time) before the execution of the code block.

Expression 2 defines the condition for executing the code block.

Expression 3 is executed (every time) after the code block has been executed.

Example

From the example above, you can read:

Expression 1 sets a variable before the loop starts (let i = 0).

Expression 2 defines the condition for the loop to run (i must be less than 5).

Expression 3 increases a value (i++) each time the code block in the loop has been executed.

Expression 1

Normally you will use expression 1 to initialize the variable used in the loop (let i = 0).

This is not always the case. JavaScript doesn’t care. Expression 1 is optional.

You can initiate many values in expression 1 (separated by comma):

Example

And you can omit expression 1 (like when your values are set before the loop starts):

Example

Expression 2

Often expression 2 is used to evaluate the condition of the initial variable.

This is not always the case. JavaScript doesn’t care. Expression 2 is also optional.

If expression 2 returns true, the loop will start over again. If it returns false, the loop will end.

If you omit expression 2, you must provide a break inside the loop. Otherwise the loop will never end. This will crash your browser. Read about breaks in a later chapter of this tutorial.

Expression 3

Often expression 3 increments the value of the initial variable.

This is not always the case. JavaScript doesn’t care. Expression 3 is optional.

Expression 3 can do anything like negative increment (i—), positive increment (i = i + 15), or anything else.

Expression 3 can also be omitted (like when you increment your values inside the loop):

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JavaScript Range How to create range in Javascript

Now take the leap of faith, assume that range(start, end) will just work. Then how do we solve the problem range(start, end) ? Simple! Just do [start, . range(start + 1, end)] . So combining both, we get

function range(start, end)  if(start === end) return [start]; return [start, . range(start + 1, end)]; > 

A lot more elegant than the for-loop solution in my opinion. But we could even go further if we use new Array(n) which creates an array with n elements. If we have an n element list, we could build a range from it by mapping each element to its index, i.e. arr.map((_, i) => i) . However, according to https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/map#Description, map will not call for unassigned element. This mean we need to initialise the new Array(n) before mapping. One standard technique is to use fill . The final result is the following.

function range(start, end)  return (new Array(end - start + 1)).fill(undefined).map((_, i) => i + start); > 

function range(start, end)  return Array.from( length: end - start + 1 >, (_, i) => i) > 

Thank you Step for mentioning about efficiency when handling large ranges, which essentially build a huge array. We could have a more efficient way of doing this by using generators.

function* range(start, end)  for (let i = start; i  end; i++)  yield i; > > 

We could use this generator in a for. of loop (which would be very efficient) or use an array spread to retrieve all values (note that this essentially builds the array which is essentially the same as the non-generator approaches.)

for (i of range(1, 5))  console.log(i); > /* Output * 1 2 3 4 5 */ [. range(1, 5)] // [1, 2, 3, 4, 5] 

function* range(start, end)  yield start; if (start === end) return; yield* range(start + 1, end); > 

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JavaScript Range Functions: Generating and Checking Numbers Between Ranges

Learn how to generate and check numbers between ranges in JavaScript using for loop, range() function,&& operator, Math.random(), vanilla JavaScript, Lodash and tips and tricks for optimization.

• I. Introduction
• II. Generating a Range of Numbers in JavaScript
• III. Checking if a Value is Within a Range of Numbers in JavaScript
• IV. Generating Random Whole Numbers in a Specific Range in JavaScript
• V. Other Helpful Methods for Working with Ranges in JavaScript
• VI. Tips and Tricks for Working with JavaScript Range Functions
• VII. Conclusion
• How to generate random numbers between a range in JavaScript?
• How to get numbers between two numbers in JavaScript?
• How to get range of numbers in JavaScript?
• How do you check if a number is between a range?

As a software developer, you may need to work with numbers between a specific range in your applications. JavaScript is a versatile programming language that provides several methods for generating and checking numbers between ranges. In this article, we will explore the different ways to generate and check numbers between ranges in JavaScript.

I. Introduction

A. Importance of getting numbers between a range using JavaScript
Generating numbers between a range is a common requirement in software development. It is used in various applications such as generating pagination links, creating charts, and more.
B. Explanation of key points, important points, and helpful points
In this article, we will cover the different methods to generate numbers between ranges in JavaScript. We will also discuss how to check if a value is within a range of numbers , generate random whole numbers in a specific range and other helpful methods for working with ranges in JavaScript.
C. Brief overview of the methods to be discussed
The methods that we will discuss in this article are:

• Using a for loop to generate a range of numbers
• Using the ES6 function range() to generate a range of numbers
• Using the && operator to check if a value is within a range of numbers
• Using the Math.random() function to generate random whole numbers in a specific range
• Creating a range of numbers with vanilla JavaScript
• Mapping a range of numbers to another range in JavaScript
• Checking if a number is between two values using Lodash in JavaScript

II. Generating a Range of Numbers in JavaScript

A. Using a for loop to generate a range of numbers
One of the simplest ways to generate a range of numbers is to use a for loop. A for loop allows you to create a loop that executes a specific number of times. You can use the loop to generate numbers between a specific range.

Here is an example of how to generate a range of numbers using a for loop in JavaScript:

function generateRange(start, end) < const result = []; for (let i = start; i return result; >console.log(generateRange(1, 5)); // [1, 2, 3, 4, 5] 

• Not as efficient as other methods
• Limited to generating ranges with whole numbers only

B. Using the ES6 function range() to generate a range of numbers
The ES6 function range() is a built-in method in JavaScript that generates a range of numbers. It takes two arguments: start and end. The start argument is the first number in the range, and the end argument is the last number in the range.

Here is an example of how to use the range() function in JavaScript:

function generateRange(start, end) < return Array.from(, (_, i) => i + start); >console.log(generateRange(1, 5)); // [1, 2, 3, 4, 5] 

III. Checking if a Value is Within a Range of Numbers in JavaScript

A. Using the && operator to chain two conditions
The && operator is a logical operator in JavaScript that returns true if both conditions are true. You can use the && operator to check if a value is within a range of numbers.

Here is an example of how to use the && operator in JavaScript:

function checkRange(num, start, end) < return num >= start && num console.log(checkRange(3, 1, 5)); // true console.log(checkRange(7, 1, 5)); // false 

IV. Generating Random Whole Numbers in a Specific Range in JavaScript

A. Using the Math.random() function to generate random numbers
The Math.random() function is a built-in method in JavaScript that generates a random number between 0 and 1. You can use this function to generate random whole numbers in a specific range.

Here is an example of how to use the Math.random() function to generate random whole numbers in a specific range in JavaScript:

function generateRandomNumber(min, max) < return Math.floor(Math.random() * (max - min + 1) + min); >console.log(generateRandomNumber(1, 5)); // 2 

V. Other Helpful Methods for Working with Ranges in JavaScript

A. Creating a range of numbers with vanilla JavaScript
Vanilla JavaScript provides a built-in method to create a range of numbers. You can create a range of numbers by providing the start and end arguments to the Array() constructor.

Here is an example of how to create a range of numbers with vanilla JavaScript:

const range = Array.from(, (_, i) => i + 1);console.log(range); // [1, 2, 3, 4, 5] 

B. Mapping a range of numbers to another range in JavaScript
You can map a range of numbers to another range in JavaScript by using a formula. The formula is ((input — input_start) / (input_end — input_start)) * (output_end — output_start) + output_start.

Here is an example of how to map a range of numbers to another range in JavaScript:

function mapRange(input, input_start, input_end, output_start, output_end) < return ((input - input_start) / (input_end - input_start)) * (output_end - output_start) + output_start; >console.log(mapRange(3, 0, 5, 0, 100)); // 60 

C. Checking if a number is between two values using Lodash in JavaScript
Lodash is a popular JavaScript library that provides several utility functions. You can use the _.inRange() function in Lodash to check if a number is within a range of numbers.

Here is an example of how to use the _.inRange() function in Lodash:

const _ = require('lodash');console.log(_.inRange(3, 1, 5)); // true console.log(_.inRange(7, 1, 5)); // false 

VI. Tips and Tricks for Working with JavaScript Range Functions

A. Using appropriate naming conventions and commenting your code
When working with JavaScript Range Functions , it is important to use appropriate naming conventions and comment your code. This makes your code more readable and easier to understand.

B. Following best practices for optimization and error handling
You should also follow best practices for optimization and error handling when working with JavaScript range functions. This includes using efficient methods and handling errors appropriately.

C. common issues when working with javascript range functions
Common issues when working with JavaScript range functions include generating non-integer numbers, using incorrect arguments, and not handling errors appropriately.

VII. Conclusion

A. Recap of key points, important points, and helpful points
In this article, we covered the different methods to generate and check numbers between ranges in JavaScript. We discussed how to use a for loop and the range() function to generate a range of numbers, how to use the && operator to check if a value is within a range of numbers, how to generate random whole numbers in a specific range, and other helpful methods for working with ranges in JavaScript.

B. Importance of using appropriate methods for generating numbers between a range in JavaScript
Using appropriate methods for generating numbers between a range in JavaScript can make your code more efficient and easier to understand. It also helps to avoid common issues when working with range functions.

C. Future advancements and considerations for working with JavaScript range functions
JavaScript is a constantly evolving programming language, and new advancements and features are always being added. It is important to stay up to date with these advancements and consider them when working with range functions.

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