javascript variable receiving output of function inconsistently

user_3095465 0
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Need a bit of help, I have a variable equal to a function, and sometimes it wont resolve and I can't determine why. The code should write pair of names, and array.slice should slowly pair down the arrays, while I also shrink the random number to fit inside the size of the array. I'm hoping someone is going to tell me im missing something obvious. Edit: d and e in the above code are 50/50 either equal to a name from the array or equal to nothing. This is what i can't determine.

var familymembers = ["Frank", "Todd", "Bill", "janice", "marco", "tilly", "monk", "francisco", "james", "bill", "gary"];
    var selectedfamilymembers = familymembers;
    var itemlength = (familymembers.length);
    var m = familymembers[1];
    var n = selectedfamilymembers[1];
    console.log(m);
    console.log(n);
    
    
    function christmasselector (array1, array2){
    let d;
    let f;
    for (var i = array1.length - 1; i >= 0; i--){
    console.log(itemlength);
    
    a = randomizer(itemlength);
    b = randomizer(itemlength);
    
    //console.log(a);
    //console.log(b);
    
    
    
    d = (remover(a, familymembers));
    e = (remover(b, selectedfamilymembers));
    console.log( "d = " + d);
    console.log("e = " + e);
    //array1.splice(a, 1);
    //console.log(array1);
    
    //array2.splice(b, 1);
    //console.log(array2);
    
    itemlength = itemlength - 1;
    
    console.log(d + " -> " + e);
    
    }
    }  
    
    
    function remover(selectedspace, array){
      console.log("The selected number is " + selectedspace);
    return array.splice(selectedspace, 1);
    }
    
    function randomizer(rnumber){
    return (Math.floor(Math.random() *rnumber));
    }
    
    
    
    christmasselector (familymembers, selectedfamilymembers);

javascript
2 Answers

I think you are manipulating the same array with 2 different references, you need to clone the familymembers before you assign it to selectedfamilymembers, thats what I do with var selectedfamilymembers = [...familymembers];

var familymembers = ["Frank", "Todd", "Bill", "janice", "marco", "tilly", "monk", "francisco", "james", "bill", "gary"];
var selectedfamilymembers = [...familymembers];
var itemlength = (familymembers.length);
var m = familymembers[1];
var n = selectedfamilymembers[1];
console.log(m);
console.log(n);

function christmasselector(array1, array2) {
    let d;
    let f;
    for (var i = array1.length - 1; i >= 0; i--) {
        console.log(itemlength);

        a = randomizer(itemlength);
        b = randomizer(itemlength);
        //console.log(a);
        //console.log(b);
        d = (remover(a, familymembers));
        e = (remover(b, selectedfamilymembers));
        console.log("d = " + d);
        console.log("e = " + e);
        //array1.splice(a, 1);
        //console.log(array1);

        //array2.splice(b, 1);
        //console.log(array2);

        itemlength = itemlength - 1;

        console.log(d + " -> " + e);

    }
}
function remover(selectedspace, array) {
    console.log("The selected number is " + selectedspace);
    return array.splice(selectedspace, 1);
}

function randomizer(rnumber) {
    return (Math.floor(Math.random() * rnumber));
}
christmasselector(familymembers, selectedfamilymembers);

user_47733540

Arrays are reference types in JavaScript. When you splice selectedfamilymembers there also splice familymembers

From this tutorial by “Dynamic Web Coding”, on values vs references:

That means that if you assign an array to a variable or pass an array to a function, it is the reference to the original array that is copied or passed, not the value of the array.

Try like this.

var familymembers = ["Frank", "Todd", "Bill", "janice", "marco", "tilly", "monk", "francisco", "james", "bill", "gary"];
var selectedfamilymembers = familymembers.concat();
// var selectedfamilymembers = [...familymembers]; this also works

// var selectedfamilymembers = familymembers.slice();   this also works
var itemlength = familymembers.length;

function christmasselector (array1, array2){
    let d;
    let f;
    for (var i = array1.length - 1; i >= 0; i--){
        console.log(itemlength);
        a = randomizer(itemlength);
        b = randomizer(itemlength);
        
        d = (remover(a, familymembers));
        f = (remover(b, selectedfamilymembers));
        
        itemlength = itemlength - 1;

        console.log(d + " -> " + f);

    }
}  


function remover(selectedspace, array){
  console.log("The selected number is " + selectedspace);
  return array.splice(selectedspace, 1);
}

function randomizer(rnumber){
  return (Math.floor(Math.random() *rnumber));
}



christmasselector (familymembers, selectedfamilymembers);
user_139572830
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