Filling an array with unique random values-CodePudding

Today I have something really special, hope someone can help me.

I have this piece of code:

var names = [James, Robert, John, Michael, William, David];
var genNames = [];
    
var specialNames = ["James", "Michael", "David", "Robert"]; - (not implemented, genNames[] can't contain two or more of these names)

    for (var i = 0; i < 4; i  )
    {
        var idx = Math.floor(Math.random() * names .length);

        genNames.push(names [idx]);
        names.splice(idx, 1); - this preventing generation of two same names but specialNames is something else what I need and what I explained below.
    }

Explanation of code:

This piece of code will generate 4 random names from the array named names[] and then they will be put into the new array genNames[]. I'm taking generated values in my code like this: ${genNames[0]}, ${genNames[1]}, ${genNames[2]}, ${genNames[3]}

But what's the problem?

After generating the result, there is the chance to contain two same names from names[] list as in specialNames[] list, it's a small chance in this example but I have many of values and some values which could not be generated twice like specialNames.

What I need?

If the generated names will contain two same names as in specialNames[] array, take one of them and replace (or just deny generation of two of these specialNames[]) with another name from the names[] array.

Simplified explanation:

Random generated names(genNames[]) from names[] array can't contain two or more specialNames.

Thanks for possible solutions/answers!

CodePudding user response：

You could use Set instead of a List. Sets are not containing duplicates. Is a duplicated added to a Set the number of elements inside the set will not change.

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Set

CodePudding user response：

A good approach to avoid duplicate values while generating random indexes, is doing a while loop that checks if the value relative to the random index generated is allowed or not, and keeps recalculating new indexes, until the corresponding value is an allowed value:

    const generateNames = () => {
    const names = ['James', 'Robert', 'John', 'Michael', 'William', 'David'];
    const genNames = [];

    const specialNames = ['James', 'Michael', 'David', 'Robert'];

    for (let i = 0; i < 4; i  ) {
      let idx = Math.floor(Math.random() * names.length);
      let name = names[idx];
      // Check if `name` is a specialName AND if it's already present inside genNames array
      while (specialNames.includes(name) && genNames.includes(name)) {
        idx = Math.floor(Math.random() * names.length);
        name = names[idx];
      }
      genNames.push(name);
      setGenNames(genNames);
    }};

Testing example: https://stackblitz.com/edit/react-sd7qlh