我在将 function 添加到数组时遇到问题。 (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.

Answer 1

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

Answer 2

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);
}