JavaScript Tip: get a Random Number between two Integers
August 24th, 2010 by Tweet
In JavaScript, we can get a Random number; however, this number is between 0 and 1 which is not very useful when we want to work with integers. For example, executing the random method of the Math Object we can get something like this:
Math.random(); // 0.7427427755721524 Math.random(); // 0.001514993949523702 Math.random(); // 0.4938488937880676
Many languages like PHP has a random function which take two integers as parameters and return a number in the range of the value of the two integers. (The range include the parameters). For example we can do this in PHP:
rand(10,20); //12 rand(10,20); //18 rand(10,20); //17
We can emulate this with the following function:
function randomFromTo(from, to){ return Math.floor(Math.random() * (to - from + 1) + from); } randomFromTo(10,20); //18 randomFromTo(10,20); //10 randomFromTo(10,20); //15 randomFromTo(10,20); //20
What about using it as part of the JavaScript Core?
Most of the developers do not recommend to extend the build-in objects, because it can create confusion between developers working in the same project. However, there are a lot of frameworks that extend the built-in object like Prototype.
The way to do it is using the prototype object that is part of all objects created in JavaScript. Example:
if(!Math.prototype.randomFromTo){ Math.prototype.randomFromTo = function(from, to){ return Math.floor(Math.random() * (to - from + 1) + from); }; }
With this piece of code we can call the method from the Math Object like this:
Math.randomFromTo(100,1000) //950
If you want to go beyond, you can add a new method to the Array Object which would return a random element. Example:
if(!Array.prototype.randomItem){ Array.prototype.ramdomItem = function(){ return this[Math.randomFromTo(0, this.length - 1)]; }; }
Now we can use the randomItem method like this:.
[1,34,56,76,9,67,5].randomItem();
This would return one of the items of the array randomly.
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Teylor Feliz is a well-known XHTML/CSS/JavaScript enthusiast from Dominican Republic. He has more than 10 years experience in the computer programming, graphic design, and web development world, including 2 years teaching computer science. Teylor has a degree in Applied Sciences from the University of Louisiana and is completing a Master’s degree in IT with a concentration in Web Design and Development, at the University of Denver.
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Very informative
Thank you! Glad you liked it and thanks for your comment!
Nice Tip , thanks for sharing
Yup very informative indeed
helping information. thanks
Nice post, thank you very much.
function randomFromTo(from, to){
var temp;
if( from == to ){
return from;
}else if( from > to ){
var temp = from;
from = to;
to = from;
}
return Math.floor(Math.random() * (to – from + 1) + from);
}
function randomFromTo(from, to){
var temp;
if( from == to ){
return from;
}else if( from > to ){
temp = from;
from = to;
to = from;
}
return Math.floor(Math.random() * (to – from + 1) + from);
}
The function that I use still works with negative numbers.
Thank you!
Oh,Sorry, I do not consider the comprehensive. You‘re right~
Thank you for your comment!!
very nice, work really fine thanks for sharing
Nice one! Thanx!