![]() ![]() Return min + Math.random() * (max - min) Example: This example implements the above approach. Use Math.floor () to get the index ranging from (0 to arrayLength-1). Multiply it by the array length to get the numbers between (0-arrayLength). ('select'). Approach 1: Use Math.random () function to get the random number between (0-1, 1 exclusive). color_generator = () => an array of HSV colors (each HSV color How it works Simply add the attribute data-img-src with the url of the image you want to use as a preview, e.g:The technical reason is very boring, so I skip it but you can dig in wiki. Random Picker Use this online random picker to draw a random item from a list of things, or to pick several items randomly out of a list. So, I transformed the hue through acos function. It creates a very nice spectrum of bright and vivid colors but the problem is that in usual color spectrum red, green, blue shades are way more dominant than yellow, cyan, and purple. Fix Lightness to 50% for best visibility.Ĭolor_generator = () => hsl (360*Math.random(), 0.5 + Math.random()/2, 0.5).Create a random Saturation from 0.5 to 1 (or 50 to 100) for vividness.If necessary, you can convert hsl to rgb as already mentioned by others. For anything serious, hsl is a better method than rgb. I wanted to create very distinctive and vibrant colors (for graphing). Let h = Math.random() // # Use a random start valueĬolorArray.push(rgb2hex(hsv_to_rgb(h, 0.99, 0.99))) The next two methods are converted from Ruby to JavaScript. If I had the reputation, I would have simply commented the jsbin link I created. I figured I'd post an additional answer to this already mega-sized Stack Overflow question because the top answer has another comment linking to a Gist with the JavaScript implementation of Ankerl's logic and that link is broken (404). The top voted comment of the top answer suggests that Martin Ankerl's approach is better than random hex numbers, and although I haven't improved on Ankerl's methodology, I have successfully translated it to JavaScript. If you wish to see what this looks like in action see Simple JavaScript Rainbow Color Generator for Google Map Markers. This is ideal for creating easily distinguishable vibrant markers in Google Maps and other apps. This function generates vibrant, "evenly spaced" colours (i.e. * step: The step number, means the order of the color * numOfSteps: Total number steps to get color, means total colors 28 Answers Sorted by: 2241 It's a simple one-liner: const randomElement array Math.floor (Math.random () array.length) For example: const months 'January', 'February', 'March', 'April', 'May', 'June', 'July' const random Math.floor (Math.random () months.length) console. This is perfect for creating pop-out markers in Google Maps that have optimal "uniqueness" (that is, no two markers will have similar colors). We generate a random number from 1 to 100. To ensure the colors are distinct I avoid using a random generator and select "evenly spaced" colors from the rainbow. describe("_.My goal was to create vibrant and distinct colors. From there, it's fairly easy to assert that _.sample will return the same value, as well. In short, we'll use spyOn to guarantee that any call to Math.random() returns the same value each time. Granted, by using spyOn, our test will become somewhat aware of how _.sample works under the hood, but since we're not passing our random number generator in as a dependency (another option here), we'll just have to live with that concession. So how do we write a test which will always have the same return value? This is where Jasmine's spyOn method comes in handy. First, here's the interface that we want: _.sample() // should return a random selection of 1, 2, or 3 If the return value is always random, how will we ever write a meaningful assertion in our tests?Īlthough it might sound like a vexing problem, Jasmine gives us a nice solution. Suppose we want to write _.sample, a method which takes a collection and returns a random element. Recently, while test-driving doublescore.js, my Underscore.js copycat library, I came across an interesting problem. v Testing around Random Numbers in JavaScript ![]()
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