使用输入的Javascript随机数生成器（每个数字生成一次）

Question

I am making a random ticket generator which asks range and when pressing button generates a random number in the range of that number. The code is missing an important part: generated numbers can't repeat. Probably the use of list in Math.random is also false.

 function random_number() { var list = []; var range = document.getElementById('range').value; for (var i = 1; i <= range; i++) { list.push(i); } var random = Math.floor(Math.random(list) * range) + 1; if (document.getElementById('display').innerText = random) {} } 

 <input id="range" type="text"> <br/> <button onclick="random_number()" "delete_number()" class="button"> <span id="display"></span> </button> 

Answer 1

If supporting newer syntax or using babel, use a Set , like const numbers = new Set(); And add each generated number to a the set. The set will work so that each item is unique.

You can also find an es5 way to make a set.

Answer 2

This may not be the best method as it uses recursion, but it works. It gets a random number and adds it to a list of used numbers, making sure not to return a number that is in the array of already used numbers.

There are plenty of ways to do this, this is just one of them.

 var usedNumbers = [] var randomNumber = function () { var range = 10 // If the list of used numbers is the same as the range, we have gone // through all numbers if (usedNumbers.length === range) { console.error('Max numbers reached') return false } var list = [] for (var i = 1; i <= range; i++) { list.push(i); } var random = Math.floor(Math.random(list) * range) + 1 // If the number appears in the list of used numbers, re-run the function if (usedNumbers.indexOf(random) != -1) { return randomNumber() } // add the number to the list usedNumbers.push(random) return random } // Get a random number 11 times (last one will return false) for (var i = 0; i <= 10; i++) { console.log(randomNumber()) } 

Here's another method based on @Wainage comment of creating an array and popping the number off it.

 var upperLimit = 10 var range = [] // Add the range of numbers to the array for (var i = 1; i <= upperLimit; i++) { range.push(i) } var randomNumber = function () { // pick a random number from the array var random = range[Math.floor(Math.random() * range.length)] // remove it from the array range.splice(range.indexOf(random), 1) return random } // Call a random number 15 times // If no number, it will return undefined for(var i = 0; i < 15; i++) { console.log(randomNumber()) }