p5.js - width not defined?

var grid;
function setup() {
  createCanvas(800, 800);
  grid = {
    x1: width / 10,
    y1: height / 10,
    x2: width - grid.x1,
    y2: height - grid.y1,
    width: grid.x2 - grid.x1,
    height: grid.y2 - grid.y1,
    margin: grid.width / 10,
    //margin of each lines
  };

  background(255);

}

function draw() {
  grid();
  DDA(grid.x1, grid.y1, grid.margin, grid.margin);
}
// ......

p5.js - random(), height, and width not defined?

i saw this question and i changed my code into this but it aint work and there is an error

"Line 4, col 3: Reassignment of 'grid', which is is a function. Use 'var' or 'let' to declare bindings that may change."

im using p5.js to make grid graph