I have an issue with adding a function to an array. (JavaScript)

Question

This is the code that adds the Function (Canvas Drawing) To the sameTree array

let TreesI = 5;
    let sameTree = [];
    let randomValueX = mathR(-20, 20);
    let randomValueY = mathR(-20, 20);
    for (let i = 0; i < TreesI; i++) {
      randomValueX = mathR(-20, 20);
      randomValueY = mathR(-20, 20);
      sameTree[TreesI] = Tree7(randomValueX, randomValueY)
    }

But it didn't do anything,

The console.log output gave this

[5: undefined] (6) = $2

This is a sample of Tree7

function Tree7(startWidth, startHeight) {

  ctx.save();
  let treeObj = {
    translateValues: {
      startWidth: startWidth,
      startHeight: startHeight,
      endWidth: -startWidth,
      endHeight: -startHeight
    },
    scaleR: mathR(0.8, 1)
  }

  ctx.translate(treeObj.translateValues.startWidth, treeObj.translateValues.startHeight);
ctx.scale(treeObj.scaleR,treeObj.scaleR);

//ctx.strokeStyle = 'rgb(0, 100, 1)';
ctx.strokeStyle = 'black';
ctx.globalAlpha = 0.5;
ctx.lineWidth = 0.2;
var reduce = 2;
  //Tree drawing sample under
  ctx.beginPath();
  ctx.moveTo(0,0);
  ctx.lineTo(mathR(0,10),0);
  ctx.stroke();
  // Tree drawing sample above

  ctx.translate(treeObj.translateValues.endWidth, treeObj.translateValues.endHeight);
  ctx.restore();
}

Now after getting some answers I realised that I need to stop updating the random value ctx.lineTo(mathR(0,10),0);. The code I have currently just keeps the coordinates. Please help.

It would be nice if you post how Tree7 function looks like. — Jejun
– Jejun, Commented Apr 13, 2021 at 6:47
I can't see any return value from the Tree7 function which is leading undefined — Jejun
– Jejun, Commented Apr 13, 2021 at 6:54
If you want the results of your function calls stored in your array, your function should return them. As your function currently has not return statement, it always "returns undefined" when done. Thats why you see undefined in your array — TostMaster
– TostMaster, Commented Apr 13, 2021 at 7:18
You cannot just return multiple values like return (value1, value2, ...). A function can only return one value. So you could put all your values you wish to return into an object or an array, and then return that one. — TostMaster
– TostMaster, Commented Apr 13, 2021 at 7:32

Jejun · Accepted Answer · 2021-04-13 07:12:24Z

1

Try this to store the randomly generated position values and draw.

let TreesI = 5;
let sameTree = [];
let randomValueX = mathR(-20, 20);
let randomValueY = mathR(-20, 20);
for (let i = 0; i < TreesI; i++) {
   randomValueX = mathR(-20, 20);
   randomValueY = mathR(-20, 20);
   sameTree[i] = {"x":randomValueX, "y":randomValueY};
   Tree7(sameTree[i].x, sameTree[i].y);
}

And when you want to draw with pre-generated values after this,

for (let i = 0; i < TreesI; i++) {
   Tree7(sameTree[i].x, sameTree[i].y);
}

answered Apr 13, 2021 at 7:12

Jejun

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1 Comment

AnonymousUser Over a year ago

Worked for what I asked for, but now I realised I only gave the code to show you for coordinate location x and y. I have random generating code in the Tree7 function, is there any way I can make it give same value it got first time when I call it many times in my Animation function?

Deepak kumar · Accepted Answer · 2021-04-13 06:29:14Z

1

If you are writing sameTree[i] instead of sameTree[TreesI] it will work when Tree7(randomValueX, randomValueY) returns a function.

answered Apr 13, 2021 at 6:29

Deepak kumar

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2 Comments

AnonymousUser Over a year ago

So I did this, but technically it worked, but now it says "[undefined, undefined, undefined, undefined, undefined] (5) = $2"

AnonymousUser Over a year ago

How can the function values be inside this array?

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