Question 160416 in Javascript Question posted in
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Can I access this value in an object using a for loop in Javascript?

I’m trying to create 2D array of brick game. how I get this value of object that at defining stage, if I use this code,it returned undefined

const bricks = [];
for (let r = 0; r < brickRow; r++) {
  bricks[r] = []
for (let c = 0; c < brickCol; c++) {
    bricks[r][c] = {
      x:r*(brickWidth+gap)+10,
      y:c*(brickHeight+gap)+10,
      bLeft:this.x,
      bTop:this.y,
      bRight:this.x+brickWidth,
      bBottom:this.y+brickHeight
    }
}

accessing via bricks[r][c].x inside object not work

use x failed, it was global x, not the item brick I want

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2

Answers


  1. 0

    First you have some undefined variables
    I hope you really set them out Example: brickRow

    Second you can set the X and Y outside from the object and use that property
    This is not a correct way to use your porperty on the same object where you set it.

    const bricks = [];
let brickRow,brickCol,brickWidth,brickHeight,gap;
for (let r = 0; r < brickRow; r++) {
  bricks[r] = []
for (let c = 0; c < brickCol; c++) {
  let xTemp=r*(brickWidth+gap)+10;
  let yTemp=c*(brickHeight+gap)+10;
    bricks[r][c] = {
      x:xTemp,
      y:yTemp,
      bLeft:xTemp,
      bTop:yTemp,
      bRight:xTemp+brickWidth,
      bBottom:yTemp+brickHeight
    }
} 
}
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  2. 0

    this is undefined because this refers to this object when you call the method. You can explore more about it at this

    and to solve your problem, just:

    const bricks = [];
for (let r = 0; r < brickRow; r++) {
      bricks[r] = []
    for (let c = 0; c < brickCol; c++) {
      const x = r*(brickWidth+gap)+10;
      const y = c*(brickHeight+gap)+10;
        bricks[r][c] = {
          x:x,
          y:y,
          bLeft:x,
          bTop:y,
          bRight:x+brickWidth,
          bBottom:y+brickHeight
        }
    } 
    }

    hope it will help you.Let me know your result

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